To me it doesn't matter if it's a tag or a branch, but, as far as I can see, there are no branches for point releases. For example, there's a branch release_50, but no branch for release_501, which exists in the Subversion repository.
I might be missing something but not mirroring tags in the Git
repository seems problematic. If someone wants to build a specific
release (from Git repo), how can they know which commit on the release
branch they should use?