It happens at the very end of a massive blowout. It’s not like it’s something we do to bring the team out on to the field or a 3rd quarter pump up attempt.
I’ve been to such games several times with non-BYU fans and in EVERY case they actually think it’s really cool, especially when people all around the stadium randomly start “popping” during it. To a person they give a little chuckle and say something to the effect of “that’s pretty cool/neat”. Even objective Ute fans think it’s fun.
Anyone embarrassed by something as benign and random as popcorn popping has some serious self esteem issues. There really aren’t that many BYU game day traditions that have stood the test of time (they took away the touchdown tortillas when I was a wee lad”) but popcorn popping is a pretty cool inside joke type tradition.