I have been told by different CM that the resort, room type has to be in the discount. Most of them won't just change your ressie# though some will but not Disney policy. I even email them & was told same thing had to be ava to get discount. No longer will apply discount to existing ressie, unless they have it for the % off etc
This has been my experiences so no flame just giving what I have found out. EX I had a room only for Dec & the military discount came out. They couldn't give me the discount for my room only as it wasn't ava. But I was able to change the dates so I could use it. She even tried to change it as she talked to a GS but no luck. But I still was able to get 40% off by changing dates. Up to Disney on how they do things. MHO