GitHub added support for having multiple-forks of the same repository in a single organization. For this to work, a new parameter head_repo was added to the pull request API call.

When using this field, the head parameter must only contain the branch and head_repo must contain "organization/repository" This is not documented in the GitHub API docs 🙂

https://docs.github.com/en/rest/pulls/pulls?apiVersion=2022-11-28#create-a-pull-request--parameters

I am cooking a commit for this.