Reminds me of WinFS, the Windows filesystem built on top of a relational database [0] that was supposed to ship with Longhorn (aka Windows Vista). Neat idea that never materialized.
A full relational database for a file system is another example of the DB overkill that is common in the industry.
Teach people to use a hammer and every problem becomes a nail.
Apparently, more rational heads at MS eventually prevailed.
Which is "database as file system".