Tracking git metadata never crossed my mind (git privacy). My understanding was that metadata can’t be sole ground truths anyway. Known real–world contributors increase trust/triangulation.
Reality is not always in sync with metadata, for example; rebasing repositories as 1 commit, using different names/emails, travelling (without updating tz) or working inside time drifted virtual machines.
I’d imagine that simpler anonymization involves anonymous contributors sharing the same metadata. In short, the deniable we are one, we are many, we are legion cloak.