I’m not the parent commenter, but I think I can help clear up this confusion. Seems like you may have missed: > Or at least half a proportionality. I think the

I’m not the parent commenter, but I think I can help clear up this confusion. Seems like you may have missed: > Or at least half a proportionality. I think their idea is that in the proportion A = B, where A = w/x and B = y/z, A and B must be “of the same type.” Applied to your example, I think PC might say that in a proportionality of pressures, A and B must be of the same type—-it is not the case that w and x must be of the same type.