From what I understand, due to not being able to roll all four sides, you are limited on how high of tension you can go. I think it sort of works for the smaller screens because there's less distance to go to stretch up to tension than there is in say, a 36x48 frame. I would also hazard a guess that there is a possibility for some weird tension going on with the sides diagonally because the square bit can't pull back.
if nothing else, the square bar frames just don't get big enough for many purposes. The ones that I have are nearly for novelty to be honest. I had to modify my cameo to fit them and they don't fit on anything else aside from my manual vacuum table which I haven't used in forever.