alt Hacker NewsYou said: "If you unfold a square, you don't get two squares."
In the context of this discussion, it is reasonable to assume that any "square" available to be unfolded is something approximately like the folding phone, consisting of two layers joined by a hinge. When you unfold that, you go from having a square to having a rectangle equivalent to two adjacent squares, and usable as two adjacent squares.
I see. I agree (obviously, it's a fact), but in the context of this discussion about aspect ratios and why the golden ratio would be relevant to this situation, it is reasonable to assume that the point here is that a full-screen, unfolded image would scale exactly to a half-screen/folded image with no change in aspect ratio.