Actually false. It says that they appear 2 dimensional. Appearing 2 dimensional and being 2 dimensional are obviously different things. I don't think the FE theory really revolves either way around the flatness of the planets. They may be flat, they may be round, They could even be some other shape. Their shape doesn't change the shape of the Earth, and considering there are only 8-9 planets in the universe that we can actually observe, it wouldn't be that surprising for them to turn out to be different to the Earth. We already know the Earth is substantially different in one very key factor (we have life) - who's to say there aren't other significant differences?