One of course Alexeev was on drugs. Two 270kg does not represent his limit strength, simply what he chose to train with. Obviously he is capable of far more (if you disagree with this i'd love to see an argument as to why). This is simply representative of his training methodology, not his capabilities.
Russian weightlifter Dmitri Klokov is never seen back squatting but reports are that his "max" is 300kg. In all likelihood this is not a true max as he can be seen doing a 250kg front squat with something like a 4 second pause in the hole. It's simply not a lift they train for their sport because their programming does not call for it, and the drugs they're likely on does not necessitate it.
Max Aita has squatted 302kg at a bodyweight of 100kg but his best clean and jerk was 170kg (granted at the time he made that lift his best squat was probably closer to 250kg and at a bodyweight of around 85kg)
Further, bodyweight multipliers do not apply well to heavier individuals. That's the reason why the sinclair coefficient and wilks score exist in Olympic Weightlifting and Powerlifting respectively. There's a reason why the only guy to ever deadlift over 5xBW did it under 140lbs and the two guys that have deadlifted over 1000lbs had a multiplier of under 4xbw.