It's worth noting that we want to refine these attributes anyway in order to add availability information (i.e. express things like "this method is inlinable from macOS 10.15 on; on other OSes it should be emitted into client"). In light of that requirement and the ambiguity discussed here, a careful rethinking is needed.
See Chris's post on the original SE-0193 thread for some discussion of this as well.