I will agree that for most people in North Korea access to the outside internet is limited, but your claim that "All computer access is gated" is a stronger one, that I haven't seem evidence for.
Also, we know that Red Star OS exists, but I haven't seen any information about it's actual use. I can imagine it's used in certain sectors (e.g. education or certain ministries), but if you have information about it's usage I'd be interested to see that.
My gut feeling is that there is probably still a lot of cracked windows PCs also used in industry, but I have no evidence for that either. This is just based on how in my experience China works, and the fact that there is some business exchange between North Korea and China.
I was a whole lot better at reading the manual before the internet .