OK, I follow the reasoning. I don't squat with a barbell on my back very often. One could place this difference of opinion along with rounding the upper back in the deadlift, I think. It works, it will make a lot of people able to lift more weight, but I don't think it's as safe, either. I choose to make that tradeoff in my barbell deadlift - I do round my upper back, and I think it's a legitimate choice to make when squatting, too, so long as it doesn't cause you to get buried by a heavy weight.
-S-