What if he needs to pull some changes he needs to continue with his work?

You can merge from anywhere, not just Github master. It's a little more work, but a coworker could share their repository without much difficulty. You can even apply patches sent over email, if you're so inclined.

All legitimate solutions, I agree. The thing is, it really sucks when this happens over the weekend. Alerting a colleague in their off-hours to be able to continue with your work is not ideal. Of course, it happens rarely, so you're making a good point. If it happened weekly, that would be another story. :)

Then a local git instance would preclude him from needing or receiving those changes anyway.

Hmm, I think we understood 'local' as two different things. I understood it as a self hosted git server, like on premises in parent's company that he and his colleagues would use. Now that you mentioned it, I'm starting to think I understood it wrong.

Nope, I may have misspoke, but I meant self-hosted git instance in the intranet.