At least as of November 2018 (when I left), everything you said was still true. However!
CodeFlow was also integrated into VSTS, whose review tooling is very much inspired by CodeFlow. Reviewers could use their web browser or the client app, and it all fed into the same system.
Most of the features that set it apart from Github initially have been copied by now - comment threads with resolutions, individual reviewer states, etc, have all been recently introduced; the gap between CF and GH has shrunk substantially.
That said, CF still does a better job of retaining comment threads and associating them with lines of code. Maybe it's just different UX decisions by the product teams, but it makes a difference when reviewing complicated patches.
CodeFlow was also integrated into VSTS, whose review tooling is very much inspired by CodeFlow. Reviewers could use their web browser or the client app, and it all fed into the same system.
Most of the features that set it apart from Github initially have been copied by now - comment threads with resolutions, individual reviewer states, etc, have all been recently introduced; the gap between CF and GH has shrunk substantially.
That said, CF still does a better job of retaining comment threads and associating them with lines of code. Maybe it's just different UX decisions by the product teams, but it makes a difference when reviewing complicated patches.