Dozens? The 4chan post said "almost 6,000 internal Git repositories". We don't use git at work (TFS, yay), and we definitely aren't on their scale, but that seems high to me. Do they have a repo for every class? Is this normal?
Before per-branch controls, the only way to disable write access (while maintaining read access, pull-request privs, etc) to a repository's blessed branches was forks.
The number of git repos might look big but without knowing more, the content of most of those repos could be a complete nothingburger. Number of git repos is pretty meaningless metric, IMO.