Ofcourse they did, they essentially blackmailed the US and others from "doing Iran style Bunker busting" on its nuke program by using its massive artillery capability against Seoul.North Korea has loads of missiles and nukes. Yet they haven't really been able properly to "blackmail" Japan with it.
If Japan tries to develop Nukes in the future and Japan already has thousands of hypersonic missiles deployed against China, then it is essentially blackmailing China from not trying to militarily stop Japan.
China will have to weigh the cost of thousands of Japanese missiles coming against Chinese cities and destroying valuable assets vs Going after Japanese nuke program.
China's military intervention against Japan will not be cost free, there will be huge destruction inside China as well. So, it will require enormous level of guts for whoever is Chinese leader at the time to pull the trigger against Japan.
I am afraid China will not be able to subdue Japan without going to a costly war and it cannot allow Japan to develop nukes which will be even more costly. Cause Japan is suicidal enough to launch Nukes against China even if it means its own destruction. They are the inventors of Kamikaze attacks.
I think China needs to prepare to go to war against Japan in the next 10 years.