Why are these following Pokemon in the johto dex when they were really introduced in sinnoh?

Question

lickylicky, tangrowth, mamoswine, yanmega, and ambipom. Why are they considered johto Pokemons when they were introduced in the sinnoh

Answer 1

It's essentially because HGSS is a Gen IV remake of a Gen II game, and therefore part of Gen IV while being set in Johto & Kanto.

When the number of Pokemon in the National Dex have expanded, it's kinda assumed in the Pokemon universe that the previous regions that Ash has explored also become aware of these newly discovered Pokemon. Johto doesn't continually have 256 Pokemon in its National Dex, otherwise it'd be in the dark ages compared to the 649 Pokemon known in Unova. Of course the games themselves don't update, but it's assumed in the universe that the Pokemon newly found are made known to everyone.

From a marketing standpoint, it'd be really pointless to buy HGSS if it had the same Pokemon GSC had, when DPPt had a truckload of new Pokemon plus most of those in HGSS.

Answer 2

I think it is because you can find their previous evolution in Johto and then you evolve it and it becomes added to your pokedex. Another reason could be that the pokedex Pokemon doesn't have to be from only that region, it could be from different ones.

Hope this helps! :)

~hax