Right now in Ultra Moon, I have a male Alolan Geodude in a Heavy Ball and a female Kanto Geodude in a normal Pokeball. I thought I could breed them to get a Kanto Geodude in a Heavy Ball, but 10 eggs in they are all regular Pokeballs.

Are they not considered the same species? Why won't the Heavy Ball breed to a Kanto Geodude?

It works in Gen 8 with Galar mons bred with Kanto mons.