Most people just don't understand this point. I think people start to feel the braking stress applied to the knees as people go further down in the squat towards parallel. Their mind begins to register 'lower equals more knee stress' and people just don't realize that, past parallel, all of this pressure shifts back towards the hips. One problem is that beginners don't even have the flexibility to get to the point where below parallel is comfortable so it's a realization that they will never achieve. For people who do have the flexibility and I tell them to do a very slow bodyweight squat and actually concentrate intently on where the pressure is--towards the knees as they descend and back towards the hips as they break parallel--they will instantly get it on the first rep. 'Okay, yeah, I feel that happening.' It's a point that should be obvious to anybody, which is why I wonder why 'experts' constantly miss it. It seems to me that, if knee health is the issue with squats, then either squat full depth or not at all.