True, although it could work as an input field too, with crude parsing. A number on its own would be a track number, two numbers with a separator could be disk and track.
While manual editing does work, often I find that an album has no track data, which means opening up the edit window, focussing and overtyping the track number, then closing the window - once for each track. It would be nice if we could just edit the field in situ.