The Media Library experimental module in core introduces a generic media type "file", while File entity calls the same thing "document". For comparison, the other bundle names are consistent between the two: image, audio, video.
Why did Media Library in core decide to change the naming and precedence set by the File entity module in contrib? I'm trying to wrap my head around the domain model here, to ensure I'm thinking about a Media Library in the correct way. From an end-user perspective, an image and a video are both files whereas a document is neither an image or video, so the delineation in File entity aligns better with reality.
This decision affects modules in the contrib space that want to build features around the emerging Media functionality in core, so an understanding of the domain model and intended usage will help build things up correctly, instead of taking things in parallel and incorrect directions.