That is in terms of pixels, I have no idea if the retina display does not have "square" pixels.
All of Apple's other products with displays are widescreen, so I guess that makes them stuuuuupid....
If a 16x9 screen was wider in inches than a 4x3, in portrait mode, it would not matter that is was widescreen. It would be like holding a piece of "legal size" 8-1/2x14 paper and saying you prefer 8-1/2x11 because legal size is too skinny. Of course that would make the tablet a good bit taller. I guess I don't know what people are reading in portrait mode that can't word wrap slightly more in portrait mode without seeming intolerable.
Funny someone mentioned an A500 because I have that and the first iPad, and here is a side-by-side playing Avatar i shot awhile back that shows the screen in portrait modes would be negligibly different. Would the A500 be a little taller? Yes. But not skinnier in any significant way. Part of why that is possible the iPad's 9.7 diagonal versus the a500 10.1.