In Oracle multi-tenant architecture, is a PDB a container?
Well yes, a PDB is a container for the database objects of this PDB. However container in this context only means that it contains something (schema objects, not PDBs). This is most likely why the official names/descriptions in your listing are not named containers, even if they are. It is not (like the System or Application Container) a „housing“ for a PDB. (And to make things more confusing I would think of the Application Container more like a collection, not a container)