Point being it carries both the index (versions/pointers) and full metadata + build instructions for all packages in single repo.

The index could be split from the build and the package build defs could live in independent repos (like go or aur).

It would probably take some change to nix itself to make that work and some nontrivial work on tooling to make the devex decent.

But I don't think the friction with nixpkgs should be seen as damning for backing a package registry with git in general.