Yes, but even though I myself have created my own Linux distro, I would absolutely not be able to do that with restricted internet access, without access to the guide-books, and without the help of IRC. I suspect this would be the case for most of my developer friends as well.
The distros are not being created by independent developers and then the state uses the distros, the distros are being made by the very state itself. The same organisation that will lift internet access and guide books and send their staff overseas to get training.
That's not true. A single person can do it at world scale provided they are not trying to do something overly esoteric (though you can actually get pretty far with a Gentoo base). There are even plenty of from-scratch distros that started as a one-man show. Take the recent Void Linux for instance.