I just added the bindists. To use the prerelease, you can do this now:
ghcup config add-release-channel https://raw.githubusercontent.com/haskell/ghcup-metadata/master/ghcup-prereleases-0.0.7.yaml
ghcup install ghc 9.4.0.20220501
To remove the pre-release channel, run ghcup config set url-source '{"GHCupURL": []}' (this will not remove the already installed GHCs). More information here.