Mopidy API: LibraryController.lookup on file backend: returns bad information?

I am running Mopidy 3.0.1.
I am developping a web client using the javascript API, and I noticed that a call on mopidy.library.lookup (as described here) with a file: uri seems to return dummy results when the uri does not directly points to a file.

For example mopidy.library.lookup({uris: ["file:///home/data/M"]}) will return

{ "file:///home/data/M":
    [ { __model__: "Track", uri: "file:///home/data/M", name: "M" } ] }

The results are similar if a uri to a real folder is passed.

A call with a full track uri seems fine though.

Is this the intended behaviour ? I understand that expanding sub-uris could lead to problems if the file-system is cyclic, but it still feels strange to me to return dummy entries if nothing is found.