On Blizzard's defense, Outland is not. It is in the border between physical universe and the Nether, we don't know how that kind of positioning is categorized (is it in both? or neither?). It could be in neither, while in the process of falling into one side (Nether), but haven't fallen close enough to be saturated with Nether's energies yet. At least, in "Illidan", Outland was still counted as part of reality.