I must be missing something, because from what I can tell your screen recording does not in any way counter the claims being made in the tweet. Firstly, you do indeed see the "There's no need to download a new web browser" message on Bing. Secondly, the recording finishes just before we see the Firefox installer which is the point when, unless I'm mistaken, the "To protect your PC we recommend only running Microsoft verified apps" allegedly appears.