Most higher level Junta officials were given amnesty as part of the transition and even sit as sitting MPs, and lower level officials were also let off with little consequences.
There was no legally enforced Pact of Forgetting so people are free to discuss what happened without ramification.
The second item (actually 3rd as you structured the paragraph) I suppose answers the question raised by the first quote. I was going to ask "was there a quid pro quo whereby absolute amnesty applies to any and all acts
that were fully disclosed, deposed to the public record?" Apparently not, as the middle section quoted below also implies:
Those who suffered the most were middling officials, to weak to pose a threat to democracy but too powerful to be ignore. As such many middle ranking civil servants and military officers faced some backlash.
Excrement rolls downhill I guess. It seems outrageous to me that the persons most responsible shrug off consequences while the underlings who were following their orders take it--apparently with some considerable mitigation, but still.
Of course if one is cynical about power dynamics it has to be this way. The underlings would obey orders from the top to resist toppling the Junta if the leaders felt they would suffer accountability for what they did; the only way to get a stand-down order and avoid a red-hot civil war which the populist insurgency might well lose despite their greater numbers, and which would surely inflict tremendous human suffering and major economic damage for the satisfaction of putting the SOBs firmly and finally in their place.
I don't know anything about Spanish or other "Pacts of Forgetting," which is another risky course IMHO. The real high road for the insurgency to take would be to offer total amnesty for all, high or low, for any acts whatsoever--provided these persons sign off on putting all of those acts, even the ones that the Junta thinks they managed to keep secret, completely on the record. Any official, high or low, has a clean slate in terms of legal liability; it would even be actionable on their part if they could prove that they weren't hired or promoted because of infamy due to confessed deeds--though I suppose that is a dead letter (just as in general, so-called rights that say workers have not to be discriminated against on grounds of say age are just about impossible to prove were violated as long as the people who in fact failed to hire or promote or did something more outrageous on the face of it apparently obviously because of some prohibited discrimination, have the wit to avoid saying it openly where they might be legitimately recorded as saying it). In reality, under such a "amnesty for transparency" deal, of course the persons who did nasty things will not be favored by the majority of people who suffered for it--but in fact the number of British persons who are either pro-Junta despite its shortcomings or ambivalent and thus inclined to cut someone conditional slack is going to be quite high, especially in certain professions. So total openness is not in fact a career death sentence though it is a restriction, and an unfortunate effect going forward is to perpetuate a social split between pro- versus anti- Junta factions, one that realistically would take generations to fade out--plural generations because you can bet the offspring of pro-Junta types will be both propagandized and suffer some animosity themselves, and so a lot of them will tend to carry the grudge forward, thus associating with fellow reactionaries and being thereby an objectively hostile and threatening faction.
Also, the rules should be strict that things have to be actually disclosed, confessed to, promptly, for amnesty to apply. Anything that is kept silent that is discovered later, the bad actors are fully accountable for.
To make it easier for the Junta gang to accept these terms, I suppose it should apply to both sides. Planting a bomb in some police station could well be something the resistance people, who are I suppose not the majority but a large percentage of the non-Junta ruled population, would celebrate as heroism--but they too should be required to disclose who was involved doing what, and be liable for criminal prosecution if they sit on this information. In context, with the resistance succeeding in breaking the Junta's immediate control and putting in a new democratic regime, one would hope the insurgents are more than happy to boast of their successes and even failures in the good cause, and confident that however irate the protected, amnestied Junta types are, the net weight of the new social machinery will deter retaliation, just as they are deterred from settling private scores by the fact that such vigilante action is as always illegal and subject to severe penalties. Of course there are always fringe lunatics, people on whom rational deterrence just does not work, but with the mechanisms of law and order, the police and the courts, already having ready to hand the docket of motives vengeful types on either side might have, the work of tracking down new culprits should be eased, making legal punishment after the fact more certain, and enabling protective measures to catch such rouge actors in the act before they succeed in taking revenge.
Any other way, such as taking depositions but then sealing them, or attempting to put restrictions on what people can say for the sake of the peace, leaves too much power in the hands both of former Junta supporters who know the score of what they did and have their suspicious beliefs, true or false, about who hurt them and who to blame for their discomfiture, and also radical rebels who think the settlement is half baked and have reason to fear it cannot protect them so they have little to lose.
In fact I am taking the terror incidents already posted as evidence of just this sort of falling between stools. "Don't ask, don't tell" applied to either the Junta or the most ardent rebels seems largely to blame. If that fellow in charge of the Security forces had been required to open up all the records of all the things he did, it seems unlikely he could get away with more dirty deeds on the same lines--which I think does in fact account for some of the reactionary side of the current terror; they are in fact being covered by Junta sympathizers.
Of course this is all in context of post-Cold War but still ongoing national interest as usual global politics; by the customary rules of the game, international espionage is still ongoing, and long-established moles in various foreign nations (some hostile or largely so, say Russia, China, or Iran, others nominally friendly) would be exposed, both rendering them useless and exposing them to vicious retaliation, not to mention the possibility that they might turn in captivity and further undermine British intelligence capability by spilling their guts lest they be quite literally spilled physically. So in that context, such persons need to be debriefed behind a wall of security, which of course could be breached doing great damage despite things being kept officially secret.
But realistically that kind of thing does happen all the time, on a limited scale; meanwhile, perhaps Britain should sit out the international spy game for a while, so effectiveness in the future is not such a major priority, for a generation or so anyway. Taking care of people who served in good faith is a priority I think.
As a general thing though, transparency is obviously superior to obscurity. Trying to gag people is largely futile--it may deny people who ought to have open legal recourse their day in court, but nothing can stop people saying things the law says they shouldn't, not completely, especially if the law going forward is not once again given carte blanche to lock people up and seize things without public accountability--whereas if they are, we have another Junta, be it the same old right wing guys, who have the training, the experience and the camraderie (more or less) to take the inside track, or a bunch of newfangled amateur leftist Cheka types who will gain what passes for "professionalism" in the matter of state terror fairly quickly even if they don't actually study up on what such examples as Lavrenti Beria set for them.
I could offer the speculation that one reason the insurgents were not able to hit upon such a sweeping and absolute solution, peace for candor, is that other agencies involved in the negotiation, such as the US mediators involved, have too much dirty laundry that would be aired with complete transparency in Britain. As you as author have noted, the Coup itself is a bit of a contrived black box, but I would not find it so crazy if it happened just a half decade or so later, in the Nixon years--and the track record is that even if subsequent administrations (Carter, Clinton) found the hidden records of how it happened a bit deplorable and quite appalling in fact, the deed being done, they'd just follow in the footsteps of their predecessors and use the "asset" of a controlled British regime for all sorts of stuff that might be risky to do in more open societies. Consider for instance the carte blanche the Indonesian junta under Suharto and successors, installed with major US support in 1965 to oust the leftist-populist Sukarno, and to massacre close to half a million Indonesian Reds in short order, had to occupy and attempt to incorporate East Timor for decades after the 1975 Carnation Revolution in Portugal that turned the half-island holding loose unilaterally. The Timorese resisted, violently, for not one or two but nearly three decades, suffering massive loss of life and other terrors, while the US governments under the Ford, Carter, Reagan, Bush Sr administrations pointedly looked the other way and continued to support the Indonesian junta as assets--I am not sure if Clinton took any action to address the situation. By the time East Timor was being supported as an independent nation, former President Ford went so far as to apologize for what he now said was a culpable mistake on his part, but by the time he did the responsibility had been shared in a quite bipartisan manner! Eventually it was water, and quite a lot of Timorese and some Indonesian blood soaked in it, under the bridge. (Though I do think Saddam Hussein might have been thinking of the precedent and hoping that the US government would regard his seizure of Kuwait as a parallel case, and we are still living with the repercussions of that action of his to this day, at great cost to many people on a far larger scale than East Timor--this is why integrity in apparently small things matters).
But with that example, and others I might elaborate on, in mind, it seems very likely to me the Junta's misdeeds included not a few actions ordered in Washington DC that the US establishment is hardly ready to see disclosed, whereas making a special wall of security for catered international terror is still drawing attention where they most pointedly do not want it.