Coming from an application development and design background perhaps I hold a different perspective. Also, I first try to look for the technical difficulties before trying for fit a conspiracy theory or consider decisions of this sort being directed purely on emotion.
To me the situation feels like there is a technical design constraint where there is no way for the system to distinquish between a game loaded from a disk and one downloaded from the cloud. Once the game was ripped from the disk the image likely looked exactly the same as a digitally downloaded one. So without system DRM redesign, which they may do down the road, they would have have to temporarily drop the family sharing for the alternative "lock the disk in the drive" method. Here's hoping they can make a work-around by launch.
That's just my take of course.
