Since you know so much about how elite athletes train, why don't you read a few articles by Mike Boyle. I think he's trained a few more elite athletes than you and guess what he has his athletes do? You guessed it, he bases routines off of single leg squat variations. He doesn't even have his athletes do back squats (GASP!).
I love how you mentioned how high school athletes train. We all know high school coaches are the top of the line strength coaches, right? Hell, my high school coach had us bench and back squat three times a week, every week. You would think with all that back squatting, we'd be great. Instead, we had an entire team with kyphosis from so much benching and an average of 3 acl tears every year. Yup, that's a top of the line routine we were doing back in high school.
I'm not saying pistols are the best exercise by any means. I would never base a program around just pistols, the same way I would never base a program around just back squats. My point is that they help provide variation and are very challenging to do.
I don't know what your comment about the 500 pound squat was supposed to mean, but once you get past the high school level (where you're probably still at), 500 lbs would only be impressive for the smallest guys on the team (and kickers).