Well, did you train at commercial gyms or powerlifting/weightlifting gyms? What if the lifters just happened to be on high volume blocks, or tapering for a meet whenever you visited?
Well yea, a 4-plate ATG squat is gonna be an honest rep, probably by someone pushing 465+ for a parallel squat.
I always figured you could take most men < 45 and hit 1/2/3/4-plate on OP/Bench/Squat/Dead given 2 years on a dedicated schedule w/ a simple plan like 5/3/1. Most people get in the gym for social-hour instead of hammering it hard (aka "fuck-around-itis")