We used CS meals as snacks at POFQ last year. I went and spoke to CM at the concierge first to find out what the policy was at the time. She said that we could do so by all means but it could only be done in the food court. She then went on to explain that only places that served both meals AND snacks were able to do this trade. So the only reason they can't do it in the gift shop is that the gift shop tills are not programmed with a facility to ring up/redeem a CS meal.
We have, in the past, been able to do this at Main Street Bakery too, but last year we noticed they were incredibly strict about what you could take as a 'meal' although this could have been down to the CMs who happened to have served us at the time