North Korea would likely be more reckless than Russia or China if it had the chance.
Deep encryption is of course brilliant... until it is cracked.
As for the hacker, the sensible course would have been to bring him on board to identify vulnerabilities for them.
I believe North Korea is suspected of already probing other countries' Internet services. Sometimes I wonder if the various reported or suspected attacks from N.Korea, Russia and China are really just tests by them on their own methods and abilities. If so, it's a frightening prospect.
Yes, I agree about that hacker. Perhaps prosecuting him is just a face-saving and diversionary tactic.