the lighter you are the easier it is to squat 2 times or whatever BW. there is not a linear correlation between lifted weight and BW.
a 2 times BW squatter at 250 is much stronger than a 2 times BW squatter at 160.
for that reason powerlifters use the wilks formula to compare weight classes and not simple times BW.
regarding Alexeev: 270 was a pinky weight for him, he could easily handle well over 300 kilos. however still very few at close to 300 pounds is squatting 2.5 times BW (unequipped) while you won't win anything with a 2.5 times BW squat at 150.
times BW for a squat is just raw measurement (although tennis players all fall in a pretty small weight range from 160-180 (unless they are "freaks" like isner, karlovic or rochus on the other side of the spectrum).