The last thing Xi wants is an emboldened Pyongyang—he has managed Kim adeptly for years.
How Xi can "manage" Kim when Pyongyang already is a telephone government? North Korea is a Chinese proxy.
When China wants to increase badness against US, JP, SK, it pushes forward its pawn, and orders Kim to do something to spook them.
The independence of NK regime when it completely existentially depends on China for everything is a myth.