On one hand, to be fair, it's entirely possible Hypno could appear in a space-time distortion (it doesn't happen in game mechanics but it *could* in-universe).
On the other hand, out of the 242 Pokemon in the Hisui Pokedex, 35 of them can learn Hypnosis (36 if you count Ninetales and Alolan Ninetales separately). And on top of that, the way this is written, any old sleep move would have worked just as well.
Hypno traveling to the Hisui region just to fuck the new pokegirls is rock solid hentai lore. The girls can't hide from the yellow menace, they'll always find them.