I see. In that case, this is true of most regions. There are usually just two characters of the region's signature element: an Archon and a Reasonable Authority Figure. But in case of Natlan, Mavuika is both.
Sumeru being the exception, because it was released with the Dendro element, and they needed to quickly fill up the ranks.
Usually there is at least one or two more though. Mondstatd has both Jean *and* Sucrose for anemo. Liyue has Ningguang and the troupe girl who's name I forget as geo, people already brought up Inazuma's massive list of electro, and Fontaine is the odd man out with only having its "Archon" and Neuvillette.
Natlan has only a singular pyro character. And while I get that they want to have the tribes be varied, it just feels a bit odd to have a nation of fire only have a singular unit that uses the stuff. Especially when you factor in the whole "Flower feather is supposed to be the pyro tribe" thing, because both their units are anemo.
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For the whole save thingy, I think its fine that the saves get reset for new updates. It's the price we pay for playing this game in a vastly unfinished state. Technically speaking, you don't have to 100% every new update, you can just beat the cities and wait till we get the next update.