SU isn't trying to slow the tempo. If anything, they would prefer other teams to rush their sets because that would more likely result in poor shot selection or a turnover. In matchups where the opponent does not have a talent advantage, smart coaches elect to slow the tempo against a zone because it increases the odds of a better shot and, with proper ball reversals, forces the defense to expend a lot more energy. It's very deflating for the guards and forwards to slide for 30 seconds only to have some stiff hit a wide open 3. Truth is, just because a team waits until there are 5 seconds left to shoot doesn't automatically imply they were suffocated for the previous 25 seconds. With teams that are not fundamentally sound or prepared, yes, but any reasonably coached team (e.g. the top half of the ACC) knows that to beat a zone you don't need to take the first good shot you get... unless you want to play at a faster pace (e.g. North Carolina).
To answer your second question, the bottom third of the ACC is probably athletically inferior, and especially the majority of the non-P5 games in November and December. There's just no logical argument to play 100% zone in those matchups. It's universal knowledge that minimizing possessions favors the less talented team. So why on earth would SU want to purposely slow the pace of the game? I think JB at his core still wants to run and play fast, but his allegiance to the zone has created this Stockholm Syndrome where everything that used to matter is now irrelevant. I could be way off-base, who knows... but that's the general vibe that I'm picking up.
