StageX does reproducible builds, so they are signed independently and can also be verified locally. I don't think it applies to Astral, but it's useful for packages with a single maintainer or a vulnerable CI, where there is only one point of failure.
But I also think it'd be nice if projects provided a first-party StageX build, like many do with a Dockerfile or a Nix flake.
Once we have better support for multiarch in stagex, since StageX is distributed as OCI images, you could just replace your existing Dockerfile bases with stagex.