There's a big difference between Bahamut, the dragon, and Bahamut, the primal. Tiamat, Bahamut's consort and the person who summoned Bahamut, the primal, goes so far to say that the two are completely different. The severity of the difference is even why she's stayed in Azyz Lla this entire time.

Dragons have their own aether aspects that works differently from anything else as a result of them being aliens to Hydalyn, the planet. The main difference is whether they have more wind or earth aether or an even mix of both as that determines what type of dragon they end up being. The closer dragons get to being descended from Migardsormr, the more non-normal their forms and aether seem to get. As Midgadrsormr's children, Bahamut, Nidhogg, Hrasvelgr, etc. probably have some of the most non-normal aether of anything living. The "normal" rules of aether apply to them very loosely.