Hmm I don't fully agree with this. By using the PR workflow on GitHub, your One True Way is that people need to create an account on GitHub and use their web interface to make the review.

You always have to enforce some kind of conventions, but I wouldn't say GitHub is the most flexible. With an e-mail workflow, everyone can use the e-mail client they want and review the patches the way they want, without being forced to sign up on a website at all.