Furthermore the value of NK isn't the people, but the geographical position. It is a well known fact that China is amping up its projection of power, and using it to claim territory. Doklam is the most recent example. Furthermore I don't think China gives two shits about forcing people into doing what it wills. 25 million people is basically a negligible amount for China to handle, it's >2% of their total population. If anything it is an opportunity to gain goodwill by "rescuing" them.

All I'm saying is that perhaps China has a vested interest in trying to provoke NK into increasingly irrational decisions so to open an opportunity for them to annex NK in the name of "maintaining order".