I agree with the general point of your comments, but when it comes to a question of ‘can they actually do it?’, I would not bank on the backwardness of the NK regime as a guarantee that they cannot. First of all, the ‘rewards’ for those successfully advancing the nuclear program are likely to be enormous - especially by NK standards. There is thus an incredible amount of motivation for those involved. They also likely have access to a disturbing amount of stolen information from abroad.
I’m sure they will be able to do it at one point. But, their ability has nothing to do with being related to South Korean’s. Their ability comes from assistance from foreign sources and continuing to work at it. Time to shut it down.
Their nukular and missile technology is not home grown.