Azeri doesn't seem to be a starting culture, so it's something that will have developed in game, and in that particular variation of "history", a different Turkic culture could have been the root of it. Remember that not all cultures will diverge from (or be hybrids of) their actual in real life historical parent groups.
You can get cultures being produced by *similar* cultures (i.e. ones with the same roots) as the historical ones, but not necessarily the exact same one - and even if the culture is originally the same one, it could have changed from the historical one by being reformed by the cutlure head to replace even quite core traditions.
