Personally I don't see much reason for this to be implemented via a git repository (rather than a text field in a database, like the existing Bio text), other than "we're GitHub, everything's a git repository, so why not".
At the moment, it's a single-file repository. Perhaps they have some ideas for other things that could be served from there too.
Weirdly at the moment it's required to be a public repository. This seems counterproductive: if it's my personal information blurb I don't much want other people looking at its history and I certainly don't want them forking it. (Are there any non-malicious reasons for doing that?)