They can help indirectly, maybe giving secret tour to the facilities and stuff. It doesnt have to be Chinese technicians going to NK.
Eventually tho.. we'll see if there is any picture of foreign technicians emerging in NK facilities. But for me Chinese technology and technical assistance is the most mature NK could acquire.
It isn't that China doesn't want to be caught in their devious plan to make DPRK superpower. If it ever wanted to, DPRK wouldn't have been that poor.
It's that dead
last thing China needs is powerful and independent DPRK from American TV series.
Powerful and independent DPRK, kind reminder, started Korean War. And DPRK started it's nuclear program decades ago not just for self protection (arguably China will always intervene to save it), but for their own freedom of maneuver.
China needs DPRK populace to have just enough so there will be no refugees. It needs Korean elites to have just enough advantage over them as to make the country stable. Finally, it'll surely supply enough fuel, to ensure police cars run smoothly.
Everything else is Pyongyang's own problem, and frankly it makes China's life more difficult. DPRK, for Beijing, is a necessary problem.
For Pyongyang, all we see (from nuclear weapons to AWACS) are means to have freedom of maneuver. And students in Pyongyang, just like Seoul and Beijing, learn well over 2 thousand years of history with China - allies they are, but DPRK is deeply suspicious and insecure about China.
Remember high profile assassination in Macau.
Strictly speaking, no one in the world with the exception of DPRK itself needs strong DPRK. And the only countries that really help them just happen to be countries Kims found in their dark hour. And while Russia may indeed be much deeper in this (blood is not just ink), this whole development started no earlier that January 2023(South Korean shells opened Kim a historical opportunity he just could not resist).