This is one of those disks where the 2d and 3d are combined on one disk. If watching 2d your player only uses one of the two data streams. Similar approach to Hugo in the UK.
Have read conflicting reports on whether this gives worse picture quality than the two separate 2d and 3d encodes on separate disks the big studios do.
This title is I believe from Entertainment One and as with many of the smaller studios they do these combined disks. Is a cheaper option and means they only need 1 disk in inventory.