[the_gipsy]

Ah, got it, thanks!

IMHO, Component style (React) and State style (Elm) can be interpreted as two styles of isolating (or decoupling), just very orthogonal to each other. Isolating is a very basic necessity for keeping complexity at bay.

Component style isolation works really well for "inner UI state", like your accordion example. But it quickly gets out of hand once you get to some non-UI state that is shared between a bigger component hierarchy.

State/View/Message isolation works really well for actually keeping the views pure and having only one change-message channel. But the state model quickly (and message handler) quickly gets huge. You also cannot publish/provide a small "component" with local state.