I was shocked to read such a thing in 2025 but either there is some nuance to your observation or your information is outdated https://goharbor.io/docs/2.13.0/administration/#:~:text=or%2...

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.