This is for commits (including merges/rebases) made through the web interface. You don't need a GitHub setting for your local mail. And in any case you could just use a dedicated commit author address if you are that worried.
If this interests you then you might like to check out “They Shall Not Grow Old”[0] - a Peter Jackson movie which is based off AI/ML restored[1] WW1 footage with color, sound, and dialog added to silent B&W original stock.
Exactly this - in "Exchange" terms they called it something like "smart host" if I remember. But basically you use a major provider to do the final "connect to the internet at large" but everything is on your machine and you could change your outbound routing at anytime.
“Google Search works hard to understand the content of a page. You can help us by providing explicit clues about the meaning of a page to Google by including structured data on the page.”[0]