[squiggleblaz]

yes i think you've hit the nail on the head. I tend to view NixOS not as a distribution, but as a distribution framework. The system configuration is the sources for an immutable distribution as much as it as system configuration.

You're in no way bound by decisions of the nixpkgs contributors: as you say, we can add a patch. Or we can also decide we totally disapprove of the way they've configured such-and-such a service and write our own systemd service to run it.

Anyone can write a local debian package which adds a patch, and build and install it. And anyone can write a systemd service and use it instead of the distribution's systemd service. But on NixOS, these are equal to the rest of the system rather than outside it. Nixpkgs is just a library which your configuration uses to build a system.