Looks good! Also nice to hear it will replace search.nixos.org/flakes. I was a bit worried seeing the title that there would be 3 different similar services for flake discovery 
It enforces semantic versioning and does not currently act as a proxy .
What should be done with versions? For instance, nixpkgs, home-manager, nixos-hardware or nixpkgs-ruby: they all do not have versioned releases. Will Redirect flake pins to github tarballs 路 Issue #17 路 flakestry/flakestry.dev 路 GitHub allow adding flakes without versioned releases? Are there future plans for versioned flakes?
Edit: thinking about this a bit more, since semantic versioning was mentioned. So it might be to refer to some stable x.x.y version range. However, we already can refer to branches which seems more powerful than versions? An vx.x branch might already be just as useful? But a beta/staging branch is also possible (something that can be inconvient using version numbers). Am I overlooking something?