He only writes like a German because you happen to perceive it in this way.
I am going to assume that you mean he does not write that way, I just perceive that he does, and not that my perception actually changes the way he writes.
But, to quote the man himself:
"I have conducted this analysis from the point of view of the Germans"
Just because a historian superficially focuses on one side of the war does not mean that they necessarily support that side: see Robert Citino's work on WW2 if you are that unsure-he is perhaps the greatest critic of the traditional German way of war that I have ever read about.
I never said he did support that side, nor is my assessment that he writes like a German Staff Officer a criticism. Zabecki's academic work has almost all focused on the German Army and on staff work, most commonly on staff work in the German Army. And his thesis is actually a critique of German operational understanding in WW1. To quote his Research Objectives:
"It is not the primary objective of this study to suggest ways in which the Germans could have won World War I ,or at least could have achieved battlefield victory in 1918. Rather the primary objective is to use German offensive operations and planning in 1918 as a laboratory to examine and analyze the Operational Level of War"
This is a useful study, and an interesting one. But it is not, nor is it intended to be, a singular account of what could or should have happened in Spring 1918. It deliberately comes at the question from the German side and applies modern operational theory to the decisions taken by the Germans in 1918. Zabecki suggests alternatives that his analysis suggests would have been more effective operational targets. It does not look deeply into the plans or possible responses of the Allies, only what response they undertook to OTL's offensives, nor does it uncritically assume that its proposed objectives are guaranteed to have been reached, only that they are the better targets. It provides suggestions for follow-on objectives if the first objectives are met but it is assumed that the actual operation and timetable would be continually evaluated and adjusted based on the facts on the ground at the time.
To quote Moltke (from Zabecki) "No operations plan will ever extend with any sort of certainty beyond the first encounter with the hostile main force"
Contrary to what you are saying here, Zabecki writes that more often than not, the German WW1 Offensive Staff Plans had virtually no set objectives at all-you are clearly missing the German offensive mindset here, which was to draw the enemy into a "decisive battle" at any time and at any place and annihlate their field formations through manuever.
I am aware. However, the view on the German use and devotion to the concept of decisive battle even prior to WW1 is far from monolithic. The War itself was a profoundly challenging situation and all sides worked to adjust and adapt their ideals to the situation. So a straight assumption that the Spring Offensives were aimed at the destruction of manpower alone is, IMO, not adequately supported by the evidence.
Zabecki's summary of the German operational orders often mentions objectives, and names them. Amiens is named quite often, but Zabecki generally dismisses this (IMO possibly too quickly) as being unclear since it does not list it clearly enough for his tastes or (when dealing with Ludendorff's writings private and public) as post-facto justification. This last dismissal seems strange to me, as Zabecki's thesis never seems to establish that Amiens was accepted post war as the necessary objective, so why would Ludendorff seek to falsify his interest in it to justify himself?
Zabecki does in fact look at the operational planning of the British Army from direct, contemporary accounts at the time, which he later comes to characterize as being deficient and confused against the initial German onslaught of Michael and Georgette.
To again quote Zabecki's Research Objectives:
"I have conducted this analysis from the point of view of the Germans. I have, of course, considered and described the responses of the Western Allies - The British, French and Americans -
but I have not analyzed their plans nor critiqued their actions" (Bolding mine).
To give a final quote:
"In attempting to reconstruct the German decision-making and planning process, I have applied many of the tools and techniques of the military intelligence officer - a specialty in which I have some practical experience. Both the military historian and the military intelligence officer face similar challenges, and in many cases use similar analytical tools. ... The ultimate objective for both is to produce the best possible analysis from the best information available.
This process can be as much an art as a science." (Bolding mine)
Zabecki's thesis is a study of operational art using the German plans as a basis for investigation. It is not an alternative history manuscript. His alternatives are predicated on what he views of the best use of the resources available at the time. They do not, as a military historian might, delve into the probably responses of the Allied Armies using deep analysis of the British or French position, but rather, as a Military intelligence officer would, uses limited information on the enemies positions and strength to devise an operational plan that best uses "his own" armies tactical position to achieve their strategic goals. And insofar as that goes, I believe he has crafted an operational plan with a greater chance of strategic success than that which was pursued IOTL. However, It is a mistake to read his alternatives as a defined roadmap to German victory. My objection is, and has always been, that though the operational plan is superior to OTL, had it been implemented, it still would not have been able to achieve its objectives, due to the distance involved, the resistance of the British and French Armies, and the logistical pressure of operating so far from their own rail lines, the same factors that eventually ended the German Offensives IOTL.
To give an illustrating example, in the Second World War during the Battle of Britain the Luftwaffe shifted focus from the RAF's fighter bases to city bombing. Operational studies can, and indeed have, shown that continuing attack against the fighter bases would have been the better operational approach to meet the Luftwaffe's (and Germany's) strategic objectives. And their are tantalizing clues of them being "this close" to winning the battle for southern England with squadrons being shifted north and plans for more to be moved. Thus you occasionally have Axis timelines where this pressure is maintained which leads to a operation Sealion. However, assessments of the Battle from the British side show that even if the RAF had shifted squadrons north (which is not a certainty) they likely would have been able to move them south again to combat an attempted invasion, and the material situation throughout the battle was shifting in Britain's favour, with ultimate German victory in the campaign highly unlikley.
I believe that this POD is a similar situation. That aiming at Amiens and Hazebrouk was a better operational objective than a less focused assault is a better operational plan for a Military Intelligence officer to suggest is, I think, correct. Whether an improved operational plan is likely to succeed requires, from a military historians perspective, an equal analysis of the enemies situation. Having spent some time in such analysis' I believe that this improved German plan is still very unlikely to succeed.