This will end up being the major difference between the parks, in both the streets and houses. Universal actively frowns on involved “improv” from characters who are not paid to speak. If you are in a house (and not a barker), you have to lip synch to you trigger or you say nothing. In the streets, they want you growling, shouting, or saying approved lines. As a result, “ownership” of roles can be a challenge. It’s understandable, because the size of the event requires stricter controls to ensure guests have a generally “uniform” experience.
HoS, Busch and SeaWorld have no such qualms. The roles aren’t as strictly written and the performers aren’t as strictly supervised. The actual audition process requires improv, so they can be trusted to fill in the gaps in the character, which generally results in more creative solutions.