I'm more in favor of a move like this than I am having my required messenger app spammed with advertisements. At least this is completely optional.
It's amazing, it's so much less bloated and faster than normal messenger, and uses less data too. It doesn't have stories or the rich integration with giphy etc., but that doesn't bother me at all.
That app, ironically enough, is a major reason I'm not on FB today. When I got home and installed the standard app (at 3xx MB) and immediately felt like I was tricked into installing bloated adware. It ate my data up (comparatively) and provided me with little to no extra features beyond a prettier UI. More ads, more analytics, more shitty newsfeed clutter. I uninstalled it and haven't been back to FB since :)