Yes Zelda games are usually diverse and have lots of races/tribes but... This is a sequel to one of those using the same world. It's hard to imagine them introducing another huge set of vastly different races and locations in the same world at the same time... Right?
I dunno, it just feels like this theory ties together all of the disparate elements better in my head than anything else I've seen so far.
Again, OoT had:
Kokiri, Hylians, Sheika, Gorons, Zora, Gerudo, Dekus, (arguably the Skull Kids?).
BotW had: hylians, sheika , gerudo, gorons, rito, koroks, zora. (arguably Yiga, but those are just red sheikas)
More, but also 20 year later, and OoT made Sheika, Gorons, Gerudo up and recontextualized Dekus and Zora.
Did BotW add any new race? did i miss some?
In my book it took them to build the world with BotW so they did not expand the Tribes/Races/whatever much.
But they cant really just add a little after 6 years, the longest development ever. Heck, i was somewhat dissapointed from BotW in that regard,
it fellt to "confortable" int hat area.
If the races/tribes lived outside the scope of the world we traversed (--> underground, in the air), why could they not introduce them?
If they expect us to explore a lot of sky islands and underground caves, they need to fill them with something, and to keep it balanced,
part of it has to be new races/tribes. Its not like they are competing with the others, or that they should have been there in the first game,
since... we were not in their living space. You rarely see races above ground at other places then their home.
Lets say the may got expanded by a third (sky, underground) ->
that would be 2-3 new tribes. (and i feel "third" is a conservative estimate by all the new locations, could see 50% bigger overall, just vertically)