He's describing the workflow that Phabricator uses but not explaining the benefits very well. He also seems to be oblivious to the fact that there already exists an open source platform built to do what he's describing.
You can use phabricator (and its command line tool Arcanist) with a repository in GitHub, Gitlab, or even your own local repo host. You just configure phabricator to use an external repo as the remote (by adding a URI to it and setting the mode to "observe"). See here: https://secure.phabricator.com/book/phabricator/article/diff...
Namely?