That story about North Korea wanting J-10s is propaganda coming from South Korea. The time window is simply too narrow for anything like that to happen. Maybe the South saw how much Western anger there was about Iran getting J-10s, which hasn't happened, they wanted to stir the pot themselves. Notice these rumors only happen when "rogue nations" they say are about to be attacked? The window is too narrow to possibly happen. So all of this is the same people feeding upon their own rumor mongering taking a life of its own. For all we know this is South Korea's way to get discounted F-35s or maybe even scare the US into selling them F-22s or the technology.
I do not think as a propaganda, according to Chinese website, NK did request J-10 ,on condition it's free of charge,NK may have wanted russian jet, but the russian demanded hard cash, since NK is broke, they turn to China,possible bail them out.
this is not old news, for year, NK been recipient of Chinese military aid, in the late 60's alone, NK received 60 (40?) J-6 alone.later in the 70's J-7 .not tomention shanghai class gun boat.and t-59 tanks.
the problem is the economic and political environment has change.