China is exerting increasing levels of control over many aspects of their society, banning bitcoin is just another example. China has also implemented strict video game bans for children, limiting them to 3 hours per week and only 1 hour per day on the weekends at a nationally set time; exerted control over tech companies, both on levels of profitability and the offering of services in the country; and continues to exert tight control over the press in the country, among many other ways they control everyday society. In short, it's a hellhole.
They would definitely increase the control because when you are ruling with a dictatorship then there is no chance that you would be able to give people a bit of democracy or a bit of freedom. If people get a taste of it a little bit then you are going to have a big problem.
How could you tell people "I am going to let you be free and not be involved in your life but also I would be your dictator and you are forced to do whatever I say"? You can't do those two things together, you are either a dictator or you are not and when you are one then you can't let people do whatever they want.
Crypto is freeing, it is freeing in every nation and not just in NK or China, which means that there is no chance we could end up with a good result for the parties ruling those nations when people are so free. You can do it in USA, there is a fake democracy there (two parties, basically same people) but in China you can never do that, not in NK neither.