Not going to lie, I think I lost interest after the 3rd reference to "Nix" and there being no guide as to whether it means Unix-like, Nix (the plan9 fork), NixOS (Linux distro), Nix (the package manager) or something referred to as "The Nix Language"
Nix the package manager uses the Nix language, and NixOS is a distro built on top of it. They're all part of the same topic, and the article was talking about that.