Except that's the opposite of everything the show has always implied and extended material has said outright. Not to mention that it wouldn't make sense for the colony tribe to have the larger, more sophisticated city.

I get confused about which one is which a LOT*, so despite looking it up I bunged it up. What I meant is that the tribe that Korra, Katara et all are from is the colony tribe and the one they visit in Avatar with the Moon Princess and the large city is the founding population. Which explains why the North (?) didn't care very much that their tribesmen were getting slaughtered en masse. Because fuck those rebels.

*I have dyscalculia. It's fun because no one knows it's a thing!