I guess they are waiting for the sale to end.
Probally will not buy any games then their loss.
Uhm... they stated "Please be aware that we will contact you about the offer before December 31." So yeah, it was clear that it will take that much time to get it.
Possible reasons? They'll probably have to check each and every one about what they already own, so that they don't try to gift a game you have.
Now not taking advantage of their great offer because of this, is surely not only their loss.