Glantz was wrong about the strength of Soviet forces in front of Moscow in August and September. It would take a while to find the link where Per70 listed the numbers. German forces were also stronger in August and September, not having suffered the heavy losses taken during the Soviet offensive period. Also during 1941 German forces suffered much fewer losses on the attack than the defense, so continuing to attack toward Moscow instead of Kiev or Leningrad in August or September would actually spare losses suffered IOTL during AG-Center's defensive phase, especially given Operation Typhoon's casualty ratios. The only addition by October was 2 full strength fresh Panzer divisions, meanwhile every other part of AG-Center had been weakened during the Soviet offensives toward Smolensk in August-September and both Panzer groups were worn down from attacking toward Leningrad and Kiev despite getting some new equipment in the meantime. Plus in October right at the start the weather changed, which hampered operations throughout the month.
As to the Kiev situation in particular they really offered no thread to AG-Center. AG-South had them largely pinned down and eventually AGS would breakout into Ukraine as they did historically anyway, while 2nd army (not 2nd PG) would be continuing to attack south against Central Front, which would secure the flank of AG-Center against forces in Ukraine. 2nd Panzer Group would be fine with a large open flank given that they had one throughout OTL Kiev campaign and were heavily assaulted by Soviet forces on the flank throughout August-September by forces from the Moscow region while they were pushing on Kiev and never had a problem. Moscow flanking forces were quite a bit stronger than the forces south of AG-Center IOTL, so the flank threat would actually be less if they pushed on Moscow and had an early Vyazma pocket. Plus people seem to forget that the forces along the Moscow axis kept getting more reinforcements and equipment throughout August-September and Ukraine's industry was still pumping out equipment, but that didn't make a difference to the result either. If anything letting Moscow's massive industrial base continue pumping out weapons would be more damaging compared to letting East Ukraine continue to do so for a little while longer than IOTL.
Also Glantz is flat out wrong about the capabilities of Soviet reserve armies over the winter if Moscow falls and does not even factor in the loss in morale and transport/communication abilities if the Soviet capital is lost. Moscow also had the best heated airfields in the USSR (huge for the Wehrmacht in winter), was a huge warehouse for supplies and industry (10% of USSR's industrial output in one city, not even counting the wider Moscow Oblast), plus losing it would mean the USSR loses it's biggest concentration of AAA which then becomes German or at least is removed from the equation, which is rather huge. Plus Moscow had a disproportionate role in Soviet military production, as certain high tech industries were located there. Taking Moscow also cuts off the high capacity rail line to Leningrad, which disrupts Soviet ability to supply or draw reinforcements from that city.
Plus if the capital is lost the Soviet government is pushed back to nearly the Urals, which makes it quite a bit harder to direct the war, while Stalin would likely get heavily irrational and order a bunch of immediate and costly/pointless counterattacks and burn up reserves before they can be properly prepared and equipped, which is really bad news for the Soviets. Not only that, but the Soviet citizens of Moscow would panic like IOTL and flee the city to avoid the Germans (like in most cities in the USSR when they had time to flee) and having 1-2 million refugees flooding the streets and trains would be a humanitarian and military disaster (see the role fleeing French civilians had on disrupting military operation in France in 1940).
Frankly losing Moscow is a blow hard to overestimate in it's impact and Glantz's comment is more wishful thinking than reality.
Russian industry was already being moved east of Moscow by this point, yes there was some left in the Moscow area but the Russians are not lacking in production capability. e.g. even in 1941 while all this was happening Soviet tank production was considerably greater than German production and the disparity only grew.
You are also assuming that Moscow will somehow be captured not intact but the soviets won't have made some effort to redeploy that AAA and supplies, or destroy those lovely heated air fields
If you not going to make a concerted push to take Leningrad than cutting off Leningrad from Moscow is less of an issue anyway,
While i agree that if the Germans don't encircle Kiev and trap the forces as per OTL those forces aren't going to suddenly leap north east and counter attack into AGC flanks. But they will be redeployable and the German will end up fighting them on the way to Moscow at some point. Basically AGS needed AGC to help to trap them, if they don't get that help or are even syphoned off to help AGC, then more of them will escape
You say Glantz doesn't factor in loss of morale and communication, but frankly it is you who keep's on assuming that these will be crippling as part of the general 'if Moscow falls the soviets lose' narrative that you don't support. It's also not just Glantz you're arguing against. But what you actually mean here is that Glantz doesn't agree with you on this, not that he doesn't factor it in
You also claim Glantz is wrong about the Soviet reserve armies, were is your proof for this assertion, or rather why are Per70's figures and the conclusions you draw from them suddenly unimpeachable just because they fit your narrative? Plus you have the far east armies being redeployed
Talking about weather the Germans lose more on the attack than in defence OTL is an odd way to assess things, first off there's unlikely to be such a hard and fast distinction between the two, and it ignores the fact that the Germans had suffered plenty of losses of operational capability while attacking in 1941. (in 6 months the Germans suffered only slightly less than they did in all of 1942)
Plus there's the fact that the pause and redeployment of AGC also allowed them to resupply and refit as their logistics somewhat caught up with them.
Either way you cut it, a single thrust will have longer unsupported flanks then OTL and leave more Russian forces about to be redeployed, either in front of them or on either side of them
Basically you are changing the German tactics but not really allowing the Russian to change theirs while threatening Moscow. or in fact just assuming everything else will play out the same. For instance you make the point about how 2nd panzer was able to do it's thing in the Kiev campaign despite it's long flank and attacks from the Moscow region on it. And then assuming that because that's true their even longer flanks will be fine if they push on to Moscow even if the situation in the south has changed. As if all flanks and attempt to pinch them everywhere are the same.
But talking about Panzers, how will the German overcome the same basic issue they had since June in that no matter how they split their advances, in order to do their job the panzers will invariably leave the infantry behind?
This is the fundamental problem with the whole "go for Moscow faster" plan, the panzers will leave the infantry further and further behind as they do that. And the longer you do that for that gap will only increase as will the risk to the panzers. Supplying the Panzers will also only get harder as your logistics will have to somehow keep up with the accelerated from OTL pace and be supplying them through territory the panzers have gone through but the Germans don't actually control yet. This is also an issue even if the panzers get to Moscow, they will need infantry to surround and hold it. This is all made worse because even if the Panzers get to Moscow before the weather kicks in in your faster timeline, how will the marching infantry? There is a significant risk of losing your panzer forces here even if they reach Moscow. The Russian aren't going to just sit there while they wait for the German infantry to catch up either! Armour might be fast, but it can't hold ground (Cities are even harder for them), especially if it's been worn down by months of constant fighting. Even in OTL and with the earlier pause, panzer commander were reporting 50%+ reduction in operational capabilities even before Typhoon.
But this of course brings us back to the central issue in all this. The assumption that if the Germans reach Moscow at any point in 1941 with more than a few panzers in any state it will instantly fall, the USSR will then either give up the ghost right then or become so paralysed by that the Germans will be given free reign to overcome all other difficulties and factors and win shortly after.
Stalin getting irrational, yes maybe, I can certainly see him ordering counter attacks, but again this idea that the Germans are going to work like clockwork but the soviets will be hamstrung by the whims of their dictatorial leadership does rather ignore reality. So again ignoring a problem for the Germans but assuming it will be in fuller effect for the Soviets isn't really very realistic.
P.S. On fleeing refugees that had been going since June with over 10m in 1941, and the soviets didn't collapse