first of all it is astronomically impossible to have a "flat" planet that can sustain life. A flat planet cannot suport an atmosphere for one thing.IMO, the planets were "flat" in MM1-5 because the primitive graphics of the day did not allow for 3D representations.
I find a few other inaccuracies in his story also, mainly having to do with HOMM3, Shadow of Death, and Armageddon's Blade.
Also he fails to mention (I guess this was because his story was written before MM9 came out) the connection between Armageddon's Blade/SoD and MM9.