The MutableData data type is a key-value store data type but it’s not CRDT yet, so it needs to be migrated to become CRDT and the name proposed (again as per the discussion in [RFC] Data Types Refinement) is Map.
The NRS Map is not a data type, it is just content that has the mapping from NRS names to links which is stored on a Public Sequence data type now. We could consider later on to use the Public Map as the storage data type for NRS Maps if it makes more sense than keep using the Public Sequence for it.