That's missing the point. The idea is that the Han people are who presently live there are a different ethnic group, and it really has very little to do with whoever was living there before those areas are sinicised. Which is not entirely baseless. Different regions do have distinct identities, which this map approximates. It's just that the people see themselves as Han first, so there's not really any support for independence.Yeah, the same reason explains the existence of Yuyencia, Tshiechuria, Chianghuairia, Chingchuria, Wanchowria, Kuanlungnia and Yehetland.
Like, ok Bashuria had perhaps a long time ago two ethnicities related to the modern Chinese ethnolinguistic groups, possibly a Western Branch, that would come complete a Southern and a Northern one, and Yehetland would have significant Hmong and Mien populations, but all those others have been almost all Han inhabited for centuries and centuries.