Of course, this sort of unfiltered access is still extremely restricted: these are the children of the elite, the literally hereditary elite caste (https://en.wikipedia.org/wiki/Songbun), who are investments for the state for being sent abroad for the hacking campaigns (https://www.bloomberg.com/news/features/2018-02-07/inside-ki...) or for the domestic surveillance apparatus. (Someone is developing all of the clever ways they have to restrict and monitor smartphones: https://www.gwern.net/docs/technology/2017-kretchun.pdf And it'll keep going. 'Reducing traffic jams' my arse. But at least we have more 'transparency' now...)
They are granted access for that purpose, and they know their families' welfare and positions are hostage, and are in no hurry to jeopardize their charmed lives in Pyongyang. You don't live in Pyongyang, be taught English, go through university there through to a master's, without absolutely impeccable credentials and a lot to lose. It is unsurprising that they rarely 'abuse' that privilege. (Think of the closed cities in the USSR, or shopping at the foreign-currency stores, or travel abroad.)