If used/implemented correctly, they don't.

* This is an optional feature via git config, with a further GitHub setting to reject commits pushed using your personal email address.

* If the GitHub setting is disabled, some GitHub-generated commits/fixups use your personal email (e.g. squash merge in the GitHub UI).

* I use my personal email in file-level copyright headers, even if the commits use the GitHub noreply email.

* I have my personal email on my GitHub profile, visible to logged in users.