Man, just mind your own numbers. The only person you should EVER be in competition with is yourself. Who gives a flip what Joe Blow can or can't do? If he inflates his numbers, the only person he's trying to truly fool is himself because most people don't give a shit. You are young and you haven't been lifting for a decade or two. That's cool man. Your progress at this point is basically limitless. If someone claims to squat 750, we have no reason to believe or disbelieve...as you pointed out, we have no proof. Fine. Who cares what someone else does?
I bench around 500. You probably can't. Should you care? No. Carnal can DL Mt. Everest. Do I care? No. We have our own goals. The ONLY lifts we should scrutinize are our own. There's a chick (A CHICK FOR CHRIST'S SAKE) that posts at another website I go to that can DL 500 @ 148 lbs. She also BP's 300+....
Point is: We are all different. Our only concern should be OUR progress.