I see China as being the real target of this. They have been getting obnoxious towards all the other nations in the region, often extending their “territorial” waters all the way up to the coast of other countries, and trying to snatch contested islands.
This is causing the others, including SKor, Taiwan, Japan, the Philippines, and even Vietnam to become much more friendly to each other, with an eye to telling China to take a hike and stay on its own turf, not try to steal theirs.
While the Norks are complaining about this, I would level odds that China will say nothing, but is really annoyed by it.
And an underlying current to this is that China has been given fair warning that if it allows Nork to go nuke, then Japan will lead the way in developing nuclear weapons directed at China.
China looks after the NK chow.
Why is anyone surprised that they act the way they do ?