Huh, that's true. The Yashou tribes clearly drifted apart at some point after the war when Fu You was the overall leader, though perhaps that's not surprising. Without the threat of the rebels to unite them it's not unexpected that they'd settle into their separate tribes again.

And yes, I guess to ZXC they're a known quantity that cause very little problems for Haixing, at least until Ya Qing sides with Ye Zun, so they're less of a threat.