I didn't say git did anything with GitHub usernames.
Yes it would, OP would hypothetically push to old user/org not realising their namespace had changed, but the key would check out, and potentially what was private would now be public.
But anyway, it was a hypothetical, and relatively unlikely, since for real damage (what should be private being public) you'd need to know or be misfortunate/lucky in happening to use exactly the right (or wrong) repo name anyway. And as I said hopefully/I assume they do wipe remove the key anyway.
Yes it would, OP would hypothetically push to old user/org not realising their namespace had changed, but the key would check out, and potentially what was private would now be public.
But anyway, it was a hypothetical, and relatively unlikely, since for real damage (what should be private being public) you'd need to know or be misfortunate/lucky in happening to use exactly the right (or wrong) repo name anyway. And as I said hopefully/I assume they do wipe remove the key anyway.