Github has a couple of "fun" behaviours:
1) It links the email address in a commit to a github user with that address no matter who committed it
2) If a commit is pushed to a fork, it's visible in every fork (including the original)
Which is how you get
https://github.com/torvalds/linux/tree/8bcab0346d4fcf21b97046eb44db8cf3…
https://twitter.com/mjg59/status/1486462124897361922
https://people.kernel.org/monsieuricon/cross-fork-object-sharing-in-git…