An economist weighs in here: https://www.38north.org/2012/07/rfrank071612/
Moreover, most institutions will systematically under rather than overestimate their economic activity from what scraps of data they do have. You wouldn't, after all, win political capital in the UN or the CIA by declaring the north korean economic model to be more successful than it really is... nobody wants to hear that.
Also, the embargoes are weaker now than they were a year ago, so I'm not sure that I would say that they have really started to bite. China and Russia both backed off the pressure after the Singapore summit, and their cooperation is essential for an effective embargo.
South Africa did give up its nuclear weapons. Complete disarmament.
I don't know why you think this comment was disagreeing with what I said.
[1]: Like most observers today, I think that the Vela Incident was not a RSA test. I tend to think it was not a nuclear test at all, which does differ from the majority opinion.