This is also how it works in Clojurescript (through Reagent/Re-frame). I don't have too much JS react experience, but I often read this kind of article and marvel at how huge the mental load is working on react projects in native JS.
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...