I doubt (but feel free to prove me wrong) that PB can support filetables using datawindows or embedded sql.
As far as "what good are they", I can't say. I can't really see a good reason to store files in a database, but this feature at least allows access to those files using standard file APIs (i.e., without having to access them via DML over a database connection). Blob handling isn't exactly easy in PB, so there is that advantage.