I disagree with two bolded parts:
1. He releases the ball well above his head (see pic below). He
starts with the ball around his shoulder, but his release point is the same as nearly every other shooter.
2. Playoff basketball is the same game as regular season basketball, albeit with more talented teams and
(slightly) more effort. The bigs that guard him, at best, are only going to close out on him barely faster than they do in the regular season. I don't see how this could cause much of a dropoff in shooting percentage. It seems vastly, VASTLY more likely that the existing difference is due to the very small number of shot attempts.
"5 years" of empirical evidence? You're trying to fluff it up to make it sound good, but you and I both know it's 85 3 point attempts.
If you can prove to me he becomes more hesitant to shoot when the moment is bigger, I will Paypal you $50. You have my word.