Spent some more time on this today and got ahold of someone at Xbox Support. They confirmed it is a licensing issue and for some reason Xbox hasn't been able to get licensing on the new episodes.
I would have thought these would have been pre-negotiated prior to Season Passes being made available for sale specifically. Personally, I own all TWD seasons on this service and I will be very disappointed if I can't get the rest of this season to go with the set.