Well it is, except for the the fact that like you say we don't have records of their leaders from the apex of their power. Tuskaloosa is still a good pick from a 'big personalities' point of view (which was something the devs were going on about when Civ VI first launched, justifying some of their more unexpected leader choices like Catherine de' Medici), would be easy to give his character a distinctive feel given the descriptions of his large imposing physique and how feared he was by neighboring tribes.
And I'd argue the issue you raise applies to most of the Native American leaders we know of from America and Canada. Of course Latin America is a different matter with more extensive recording of Aztecs, Mayans, Incas and etc. But besides legendary figures like Hiawatha, famous indigenous North American leaders are ones which made contact with colonists in the final years of their independence. Sitting Bull, Crazy Horse, Mangas Colorads, Geronimo, Manuelito, etc. We already have Poundmaker in the game, he died in prison after his men were attacked by Canadian troops who were putting down a rebellion. So I don't see how you can really insist we pick indigenous North American leaders from their heyday, because as far as I'm aware we don't really know of that many. So our options are either we go with leaders we know, we make up leaders entirely (which I don't think would be popular), or we just neglect these regions entirely which I don't think anyone here wants (I tend to get the impression people generally want more diverse civilizations covering more of the world).