GitHub Admins have more permissions on GitHub than normal contributors or even committers. There are a few responsibilities that come with that increased power.
The Ansible Team will periodically review who is actively contributing to Ansible to grant or revoke contributors’ ability to commit on their own. GitHub Admins are the people who have the power to actually manage the GitHub permissions.
When we make releases we make people go through a Release Manager Guidelines to push commits to that branch. The GitHub admins are responsible for setting the branch so only the Release Manager can commit to the branch when the release process reaches that stage and later opening the branch once the release has been made. The Release manager will let the GitHub Admin know when this needs to be done.
The GitHub Admin Process Docs for instructions on how to change branch permissions.