>>49219633>headcanonBut that's objectively true. In the first five generations, the only place where Pikachu can be found natively are in Kanto and specifically in the Viridian Forest. In Gen III, you can only catch them in the Safari Zone, which the game explicitly tells you is for catching rare Pokémon and in Gen IV, you can only catch them in the Trophy Garden, which is also stated to be just where a rich guy imports Pokémon to from other regions. It's only starting in Gen VI on forward that Pikachu are corralled somewhere special.
I think you're misunderstanding what "native to" means. Viridian Forest was the one place prior to Gen VI that didn't have an in-game explanation for why they're there. They aren't "native" to a Safari Zone or the Trophy Garden; they were put there by someone in-game.