I don’t understand this. Probably we run games very differently. It’s very rare that players make new characters partway through a campaign unless a character dies, in my games. For the most part, “Aztecs might become available later” is the same as “Aztecs don’t exist as a playable option in this setting”. Im
But also, this reads to me as one of two things, as a player.
1. The world is “smaller” than the real world. People travel less than IRL, there are no intrepid explorers making journeys that pessimistic people assume are impossible, etc. As a result, You also can’t play one of the Samurai mercenaries that were in Mexico at the same time that the Spanish Inquisition was happening, because that kind of travel isn’t a thing.
2. The PCs aren’t allowed to be special at level 1. You can’t play a Marco Polo or even one of his crew, traveling to a place that hasn’t seen outsiders in generations, if ever. You can’t be a stranger from a strange land.
That would bum me out, because if I’m not inspired by any Egyptian character concepts, even tho I love ancient Egyptian history and myth, I might be inspired by the idea of playing a character from a land that is far off and different in a way that the interplay will be especially interesting. A Viking in a Fuedal Japan game, exploring issues of honor, frith, orlog, etc, in a place that has a lot of similar concepts, but where those concepts also have aspects that are wildly different and alien, is a hook that would get me jacked as hell to play, and if you look at some of the really wild foreigner becomes a Samurai stories from actual historical Japan, including during times where Japan was very isolationist, there is a lot of history to draw inspiration from.
I’m pretty sure I didn’t miss your point, I just disagreed that the comparison was valid, or that the proposed logic followed.