Github imported project not importing PR branches

Summary

Per our documentation here, the importer will also import branches on forks related to open pull requests (How it works).

Currently when a project is imported the branch is not imported, making it impossible to merge. The forked repository's branch in the pull request is not imported.

Resulting in:

Source branch does not exist. Please restore it or use a different source branch

Steps to reproduce

1. Create a repository/branch on Github
2. Fork the repository, create branch, make changes.
3. Create PR
4. Import Project into Gitlab (original not the fork)
5. Review PR's and branches

What is the current bug behavior?

Imported project does not include PR Fork branches

What is the expected correct behavior?

Branches related to open PR's should be imported

Relevant logs and/or screenshots

Reproduced on 11.6.5, 11.7.4

Internal ZD