We have no idea how good his analysis of that data was
Having read the book, it's quite obvious his analysis is excellent. Your just dismissing the scholarship because it disagrees with your views.
nor how well he really did what ifs based on this specific POD and the result of capturing and using the Velikiye Luki-Rzhev rail line, not open IOTL and probably not figured into his claim.
Most probably they do. As a case in point: OTL the Germans captured Velikiye-Luki in August. The rail line from Riga to the city was still not completed when the . I'm also curious how the Germans are supposed to extend the line from Velikiye Luki to Rzhev before Operation Typhoon given that Rzhev was not taken until Operation Typhoon.
They'd be facing less Soviet troops and with fewer troops
Actually they'd be facing more. The Soviets could reinforce with forces that OTL were sent to Leningrad. I'm also ignoring your premise of the Germans trying to encircle the 22nd Army, since that requires the Germans to realize it was there before they encounter it (for the record: they did not, just like the rest of the Soviet second strategic echelon).
they can't/won't do the Kalinin diversion to advance on Moscow after Vyazma with flank screening forces.
Which leaves them with an even more exposed northern flank and not any closer to actually taking Moscow.
But prior to this by not diverting to Leningrad 3rd and 4th Panzer, plus 8th air corps can spend July-September ripping apart the Soviet counteroffensive
More realistically, they sit around in July-September for lack of the requisite shipping to get the fuel or ammo out for them to operate. Also, if the Germans try to attack in September towards Moscow, a number of said counteroffensives don't happen and the Germans bleed upon tougher Soviet defenses.
Can you provide a source to September mud being a problem around Smolensk?
Crewald, Page 170:
The capacity of this line [Gomel-Gorodnya] was initially small. It had just started showing signs of improvement when, on 12 September, floods blocked the roads from the railhead to the corps and forced its operation to be suspended.
The same rains also imposed delays on Guderian's link up with AGS.
I know, that's why I said instead of advancing conversion beyond the Luga the 18th/16th armies stop on the Luga river and instead convert the rail from the Baltic states to Velikiye Luki and beyond as they capture more of the line.
So largely what happened OTL. The Germans were converting every rail line they could as rapidly as they could because they needed those rail lines to sustain future operations.
That line was not advanced quickly because after it was initially captured in early/mid-July it was abandoned and fell into Soviet hands against until August and not converted until about then.
The line was advanced along with all the others. Just because Vilikiye Luki fell does not mean the Germans were not aiming to extend their rail net in the cities direction. The Germans were moving as quickly as they could.
while the Germans don't take the full 100k losses between July-August defending without Panzer/air support.
The Germans
did have panzer and air support in July-August. What they didn't have were the supplies or frontage to effectively use them. Nothing changes here.
Actually no, not all of the Baltics were originally standard gauge. Remember they were Russian gauge before 1915 when the Germans captured part of them. After only parts of them were converted; IIRC Estonia kept the Russian system entirely. In the Baltics too they had much more local volunteers with rail engineer experience willing to volunteer and help.
Yes, and? All your doing is proving that it was easier to convert through the Baltics then it was in Russia proper.
By focusing resources on moving east instead of north to Leningrad they'd be focusing conversion on something they didn't work on IOTL, not to speed up something they were already working on. By not advancing the lines to the north passed the Luga that can then use those resources to convert/repair lines from Riga to Velikiye Luki and beyond to Rzhev (instead of having to convert the lines from Smolensk to Rzhev as per OTL).
The Germans focused as many resources as they could on moving east. The entire point of Barbarossa was to move east as rapidly as they could. You can try and say the Germans could do it all you want, but we know from history that they could not, the underlying reasons they could not, and that you have done nothing to address said reasons.