The question should be which set of policies maximizes the power of the informed general citizens relative the incumbents and the irrationals (or very-very boundedly rationals).
This kind of transparent content removal is not what dictatorships do.
Is there some kind of "list of prohibited books" in NK (like the Index Librorum Prohibitorum in the 16th century)? I guess not, because anything that's not allowed is by default prohibited?
Yes, at least for online content. As far as I understand it, a researcher who wants access to some out-of-country material has to manually submit a request. The censors then download the article or page, go through it, and pass it on if it's found acceptable. In addition, no single computer has access both to the global internet and to the intranet.