To be honest I have been struggling to understand the relationship between the PRC and DPRK. I know geopolitics is difficult and that there has been a lot of mutual aid and cooperation between the two states, but I find it hard to explain stuff like this (from Wikipedia):

China condemned the 2006 North Korean nuclear test, as well as the subsequent nuclear tests in 2009, 2013, January 2016, September 2016 and 2017. China abstained during a 2017 United Nations Security Council vote about sanctions on North Korea, leading it to be approved.

I think the point is rather that it is distinguishable for someone knowledgeable on the subject, but not for someone is not. Thus making it harder to evolve from the latter to the former.