agreed, zn

Under center, a QB turns his back to the defense for 1 sec and then re-orients himself at the top of his drop...
cool thing is if the PA is good it holds the defense for a beat and makes up that 1 sec so it kinda evens out timewise...but I think it's a stressful thing to have yer back to the defense and then whip yer head around and forced to re-acquire the defense and, possibly get surprised by an unexpected scheme.

In shotgun, a QB always has his eyes on the unfolding defense....but loses that beat due to the lack of run threat....but that evens out timewise also.
Shotgun is easier in one sense...cuz you can see in yer periphery where the defenders are dropping...yer not surprised...cept by great coverage!!

Anyway, I think the Air/Bear Raid QB types get used to no surprises by staying in shotgun and seeing everything...
and maybe their brains get used to that. Doing the steps and taking snaps from center is NOT the reason. imo
These guys are very good athletes and can adjust to that...I think there's a mental aspect of the back to the defense and then the sudden head turn/
re-orientation that causes a slower adjustment to re-seeing what/where the defenders have moved while you weren't looking. I know it's only 1 sec or just even tenths...but it can feel like an eternity wondering if everyone will be where you think they'll be based on yer pre-snap read/last corner eye glimpse one turns to make their play fake. I dunno how to explain the lack of Air-Raid QBs success in the NFL as you have noted.

just spitballin...

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