Yeah he's not a massive fan of high bar squatting, though you could take that to mean that keeping the muscles around the back tight is more important than torso angle.
For example, the coach at my gym wants me to lean more on my squats, as since my back is fairly upright, the knees have to travel out more for my hip crease to be below the top of the knee (if that makes sense). However I prefer to squat in the way that feels most natural to me (which is literally not thinking about the movement). I'd have to take a video for a more accurate assessment. I found keeping the eyes neutral and looking off at the wall preferable to looking up or down as well.
I agree Silverback - I noticed a correlation between being able to easily bodyweight squat with my feet flat and being able to squat more weight.
There is a 60 page thesis on squatting in Starting Strength if you're really keen.
I chuckled at this part of the article too : "You may even have read that elite powerlifters squat with a vertical back – some of them do, especially the ones who lift with a sumo stance in a monolift, in the triple-ply suit-and-wraps recreational federations that don't judge depth."