I think it comes down to coaching cues working or not working if we are teaching only the olympic style squat.
Some people if you tell them to sit down just can't load their hams and glutes for shit and just slide forward. Others if you tell them to sit back will turn the squat into a borderline good morning (without meaning to purposefully as a powerlifter might, I mean).
Obviously whichever it is, the knees should still be pushed out.
To whomever said the the weight in an olympic squat was on the balls of your feet, that is definitely incorrect. Could be slightly more forward than the wide box squat, but balance point is still on the back half of your foot to drive power through hams and glutes. It never moves farther forward than the arch.