>>43555184It's a little weird, but ultimately no big deal. I'm not really likely to think about it at all if there's at least some form of justification for why they suddenly show up. However, if we're talking about remakes, I prefer that they keep new Pokemon reserved for the post-game.
>>43555198Johto was a little different because the Pokemon were supposed to be newly discovered in both regions. So the implication was that, until shortly before GSC, Johto *also* only had 151 Pokemon. Like there was that one NPC who mentioned that Jasmine used to be a Rock Gym Leader, but she recently changed over in light of the newly discovered Steel type.