I was once told explicitly by GitHub Support (just as a reminder) that one person having multiple accounts is against their TOS, so there’s that. (This was years ago, not sure if TOS has changed in this aspect.)
Never heard such a restriction even mentioned, let alone enforced.
Enforced — of course not (guess why I was told), but it stands to reason that they probably won’t add a feature to facilitate TOS violation.
This becomes messy to manage, as it's not easy(as far as I know) to use the same account on your personal PC to do both personal and work work.