I think that the average coach, and many fans, buy into the verticality principle, just like they buy into anything else - when it favors their team. I can't tell you how many times I have seen the coach of the defense stand stiff as a board and hold both hands straight over their head when a foul call goes against their post player. We know the rule,and we coach to that rule. And the players know the rule too, because they make themselves as straight as possible after the contact, to show the ref that they were vertical (even if they initially brought an arm down hard onto the shooter's head
).
The issue isn't buying into a principle,but rather, seeing the game with unbiased eyes. Not gonna happen,with this or any other rule/call.