Ultra Space is a whole new universe on its own, so it depends on where Arceus began and where, and I suppose also what it governs. If Arceus is god, does it mean god of this universe or multiple? It would still make it a god, but doesn't mean it's also the god of another universe, even if it can access the multiverse through portals etc.
It would mean that ultra space has its own type of arceus and time/space pokemon. Even if Arceus remains to be the same god in both dimensions, it wouldn't make it an ultra beast BECAUSE an ultra beast is a pokemon born within ultra space, similarly dialga and palkia were BOTH born within the standard universe and thus were born as non-UB. But I suppose that also means a dialga and palkia could be a UB if it were born in ultra space too. Giratina has its own dimension that is parallel to the standard dimenstion, meaning it is just a pocket clone of our universe that's governed by discord instead of order (laws of physics).
The difference here is that dimensions, namely the distortion world, run alongside the same universe. Ultra space is probably its own universe with its own dimensions.
