Ok, so how would such a secret end up in a commit? E.g., I don't see why I would have my home address anywhere close to a code repository. Maybe if I used the wrong "secret" email address when authoring the commit?

If it's not possible to invalidate your compromised software secrets, I would argue that you have bigger and more urgent problems to fix. But fair enough: Deleting them from GitHub might reduce the impact in such cases.

That's just an example... To give a more real example, I have accidentally committed and pushed my own private data (e.g. from my private social feed) used in testing. That could include my address too, so the example was quite possible to begin with.