Clearly horizontal space is going to be more constrained than vertical space if you put two windows next to each other horizontally, as you're going from 16:9 to 8:9. But if you stacked them vertically, well obviously vertical space would be even more constrained than that, to the point where it's so useless you don't even think about doing it. So this is an argument for vertical space being more scarce than horizontal space actually.