This is the way Elm works and I believe some people used or advocated for using Redux in this way early on. It never really caught on in React apps in my experience but it makes some interesting debugging methods easy to implement.
I never thought of the existence of the global db as the thing that ALL state should go in., or is that a community best practice?
Edit: after digging through the re-frame docs themselves, you can see here that local reagent atoms are used for local state even with the global app db: https://github.com/day8/re-frame/blob/69a3fcd411369fff65404e...