RCID is a type of local government, and those charge for parking all the time. City of Orlando owns thousands of paid parking stalls in multiple structures, and the practice is very common.
Was there something specific about the deal between Disney and RCID that specifically forbid paid parking? That would be fascinating if true.
I've always assumed that paid parking was inevitable at Disney Springs, eventually. Hell, even the outlets just up the street charges for parking in most of their spaces these days. Just because the entry and exit areas don't have booths, doesn't mean they can't use license plate readers on entry and install booths on exit. And the curious ramp configuration on the Grapefruit garage has to be on purpose...