>>26802380Exactly, it's up to the trainers who want to complete the pokedex to piece everything together and understand the origins of each pokemon by themselves, there's no other way to know, and even if you complete the pokedex, there will be more pokemon species discovered that will interact with already discovered species, which means the pokedex WILL ALWAYS NEED TO BE UPDATED
>>26802386RBY are canonically really early in the games timeline, it was a time where we, the players in the Kanto region did not know about pokemon species besides the ones in Kanto because our technology didn't allowed us to know, Kanto is a small rural region, it makes sense.
Eventually Oak wanted to get his ass off his chair in his office and actually advance the investigation of the pokedex and went to the Sinnoh region, by being there and having a national pokedex, the Kanto region now knew about pokemon from other regions and logically the pokedex entries were updated.
