>>50804130>>50804144They weren't just raised a certain way, the environment is what determines a regional evolution.
The Hisui forms are adapted to the specific environment of Hisui. There's something about Hisui in its state at that time that caused them to evolve otherwise they could just evolve in modern Sinnoh.
By your logic a Cubone raised in any old Marowak graveyard could become its Alolan Form or feeding Pikachu pancakes from any region will result in a new Raichu.
