The provided map IS the store for descendants — the host's entries are not visible. The default: a viewer that scanned its own corpus is describing a different file space, not adding to the platform's.
The provided entries are layered OVER what is already in scope: a path the provider does not name still resolves to the outer store's value. For a viewer that augments the app-root scan rather than replacing it.
How a provided store combines with the one already in scope.