Your post is very ignorant. 450 Bench and 600 Squat are HUGE for 99.5% of people. For a 200 lbs person, that's 3x bodyweight. Do you have any idea how much that is? It's HUGE! Many will never reach that, I probably never will, no matter how hard and long they workout. And those who reach that levels spend multiple years of very dedicated training in order to do so. Reaching those numbers is not something you can do on the side and with ease.
Besides, a guy squatting 600 could very easily improve greatly in one legged sqautting over the course of few months, since the amount of force needed for one rep of 1-leg squat is such a small portion of his 1RM. A guy squatting 600 probably has solid work capacity and has been working on his GPP, too. On the other hard, a skinny guy squatting one legged reps couldn't probably walk out 600 pounds. Just like it would be much easier for a muscular, strong guy to improve his endurance, then it would be
for a small guy to improve strenght and build some size.
And, who the hell said to throw out high reps from ALL training? Many PLers do high reps, usually for assistance exercies. But, when someone is injured, what good is to decrease the load only to push the envelope with high reps nearing failure?