This is a pattern I've seen in teams to enforce review of code before it's merged. You can make the main repo read-only for most of the team and require PRs be submitted from their own forks. Then, someone with write access on main repo can review and merge the PR. I think this is overkill, personally, but just want to point out that maybe this team was employing this process, rather than them not knowing how to create PRs from a branch.