Well, never mind. While they could do what I suspected, the reason for their deployment right now is rather more practical:
Unwilling to try and coerce North Korea into behaving and getting its economy in order, China is now trying another approach. China has obtained the right to explore for new mineral deposits in North Korea, and then build mines and handle the exports. China has pushed back in the past when North Korea tried to cheat on economic deals, so Chinese economic investments like this would be pretty safe. China has also obtained North Korean agreement to the stationing of Chinese troops at these new facilities, further limiting North Korean ability to play their usual stupid games.
Little islands of Chinese-guaranteed economic activity won't do much to slow down the accelerating downhill run of North Korea's economy, but this concession by North Korea does show how desperate and weak Pyongyang is getting.
Oh, and does anybody else find it funny that China has "treaty ports" in North Korea now? Which, given what happened in the originals, doesn't actually undermine my original theory at all, eh?
