In contrast, it doesn't happen with a denormalized, UI-agnostic state:

Isn't it the other way around? the UI-agnostic state IS the normalized version; the UI-aware state ready to be consumed is the denormalized one.

The choice is pretty simple to me: keep the State normalized, de-normalize it in selectors for consumption in the UI. Those selectors will look pretty much the same as the reducers you'd be writing anyway.