Be interesting to hear what's really gone on with this.
The store listing from a couple weeks away showed pretty clearly that MS has developed this feature for the X1, but clearly they are holding back on deployment for some reason. The most obvious answer seems to be that particularly early in a console life-cycle, they rely on retailers to build a hardware userbase and so they bend to the will of retailers a bit.
So, perhaps they are waiting to roll it out to users when there are more X1's sold (the fall maybe?)
Personally, it's a damn shame. I have no interest in having physical copies of games, and not having this doesn't prevent me from doing all digital copies of games, but it would be a nice feature to have.