And just why would they do that? The only reason China supported North Korea historically is because they don't want US troops at their doorstep.

Puppet states, influence, a thorn in the Japanese side. Why would China need or want Tibet or Xinjiang? Remote regions without Han populations.

I’d say Tibet is for water. The Chinese built many dams and several big rivers which flow through several countries originate there.

Well, not just water. Tibet is a high plateau overlooking the Chinese plains. It's an obvious entry point for a land invasion into the Chinese heartland. Xinjiang is a mountainous and desert region with a similar role.

I know why they're doing it, it's just cynical for the locals.

Similar story for Korea, if you're a great power, wouldn't you move the possible battle like a few hundreds of kilometers away from your capital? You would.

It would still suck for the locals.

Are you willing to bet on this?

Possibly, but why?

Because it's easy to think cynically when nothing is at stake, when you don't have skin in the game. I bet $1000 that China won't help North Korea to invade South Korea. Bet ends 2030. You in?

I would be, but there's one condition: the US pulls out of any military alliance/support for South Korea.

Chine will obviously not risk another Korean War, there's nothing for them to gain. If South Korea loses US support, yup, I'll take that bet in a heartbeat.

Deal.