I was thinking yokes yesterday too Aris. Maybe he just wanted to see me get stapled?! No he was more genuine than that - when I said no way to him, his simplistic explanation was : with good form, the weight is centered over middle of the feet, the back "straight" taking all the weight (back-hips actually), and this is maintained throughout the squat.
Maybe he was repeating an old-strongwoman tale? Don't argue with them...
If anything, I agree Rickard, it is a good psyche-up tool.