I'm not exactly sure how that works when you have a pinned one like:

$ nix registry list
system flake:nixpkgs path:/nix/store/z7gkn604dsdfdybi16hlkidj0ipnw2ia-source
global flake:nixpkgs github:NixOS/nixpkgs/nixpkgs-unstable

$  nix registry list | rg -i nixpkgs
system flake:nixpkgs path:/nix/store/c39q7pww80997lz0fyqxpvsr29q6f7ld-source
global flake:nixpkgs github:NixOS/nixpkgs/nixpkgs-unstable

That seems to match more or less what I'm seeing too then, interesting.