The lack of OIDC support for Harbor has been the biggest annoyance for me. I'd love to be able to push from Github Actions to Harbor without needing robot users.
You're mixing up Human OIDC and Machine Flow OIDC. You can use OIDC to log in as a user, but you can't use OIDC to allow federated trust from something like Github Actions.
If you can find an example of OIDC with Github Actions and Harbor I'd love to see it.