I thought it was common knowledge that the starters were just random mons the professor has on hand considering how rare it is to see starters used by normal trainers. The anime pushed the idea that everyone from a town/region got to choose a starter but that was never a thing in the games.
>>46416679OP's question is so mind numbingly stupid though, not only is the concept of starters just a gameplay thing and not a lore thing, the Pokemon in question aren't even native to Sinnoh, meanwhile you see the actual Sinnoh starters in the wild. The Pokemon in the OP were clearly chosen to fit the theme of the game and that's really all there is to it.
