Some good points and very entertaining watching your reaction. All I would say is that while squats like that aren't doing much, I don't necessarily think you need to go ass to grass to get excellent leg growth. Due to my inflexibility and my stubbornness to put the time into fixing it I suspect you'd have got pretty angry watching my depth too. It was a lot better than that guy but not to parallel a lot of the time but my legs grew very well and were my stand out body part. However my knees aren't so good now. How much of that is due to heavier weights with a restricted ROM I don't know although, I'm sure it's not the only factor but I don't suppose I've done myself any favours either, but part reps can without doubt gain muscle (as long as they're not daft like that vid).