Xfinity On Demand not supposed to work on TCD750500

I've a Premier 4 that I've had Xfinity TV on for years without problems. Recently decided to give the Xfinity OnDemand app a try, but when it tries to play the actual content it comes up with a CableCard screen. I called up Comcast and was told that my model (TCD750500) was not supported for OnDemand but the other Premier/4XL, etc. were. ?!?

Can somebody confirm for me that Xfinity OnDemand works on the TCD750500 so I can get on their case again?