I had GS as a kid. Well trained, they are great pets and well behaved.
The problem is the parks have no clue if your's is well behaved or a monster. From a liability perspective, a frenzied chihuahua is unlikely to do serious damage. A quick nip from a GS or a rottwieler can do seriuos damage. Based on the claims, insurance companies know the big payouts come from these breeds and react accordingly.
If it's a service animal, you should be stating up front that it is a medically neccessary service animal. Don't make the staff puzzle out what is going on and then get mad at them when you failed to make the situation clear up front.
As far as just showing up late and hoping they overlook it, that's rude. Most likely it's a low level employee manning the desk late in the evening and you are putting them into a difficult situation. They want to help someone in a difficult situation but it's against the rules. When the owner finds out, your risk is limited to being asked to leave, they may lose thier job. Have multiple backups planned or stay at a rest area or walmart if you can't find a park that accepts your dog.
