If I order a catalog house from a manufacturer that does prefab it would probably either mean completely prefabbed wall panels, i.e. wall panels with a handful of layers (timber framing, OSB, plasterboard, wind/moisture barriers, lathing, external panel with a base paint), plus roof trusses. Or it could mean just the framing (wall panel timber frames and roof trusses). There would be passages for vents etc but you wouldn't see entire prefab "rooms", or even prefab walls with e.g. tiles or fittings like plumbing or electrical, like you see e.g. in large hotels or cruise ships.