Git commits have a email address as a required field[0], although some people put something bogus in there. And then it's in the data provided when you clone the repo onto your machine even if you aren't using the GitHub APIs.

To his point, you can set that to the no-reply email address GitHub gives you if you don't want mail but do want the commit to be linked to your GitHub account.

[0]: https://git-scm.com/docs/git-commit#_commit_information