Then your first point is:
> No more context-switching
> Pull requests will create an ephemeral Slack Channel where all the work will be done and imported from Github. Stop wasting time jumping from Github to Slack.
But the video next to it shows... constant context-switching/jumping between Slack and GitHub.
For everything one has to say about a PR this introduces a choice between a GitHub comment and a Slack message, where comments on GitHub get mirrored to Slack but not (directly) vice-versa. Why not just keep the conversation on GitHub?
Do comments seem too "formal"? Are GitHub's notifications not targeted enough? Those seem like possible problems, but is splitting the conversation space really part of the solution?