it’s the claim of it being a file system that’s throwing me. obviously nbd but maybe my mental models broken again.

http://tom7.org/harder/

File system is the wrong word. What they should have used is file format.

It is not wrong that you can have a file (bits and bytes encoded in the shape described by a file format) on some remote point. If you have an index of those files where you can programmatically choose between multiple files that could even pass as a crude "file system". But I doubt this is what they meant to refer to.

It is likelier they wrongly assumed a file system is the system in which a file is organized, where in fact they meant file format.