The only real problem when using a dogbone to adapt your 30A service to a 50A breaker is the power cord won't be adequately protected.
You should have a 30A main breaker in your coach to protect it, regardless of whether or not you plug into 30A or 50A service. So in reality, the only item not adequately protected is the power cord between the shorepower pedestal and the 30A breaker in your coach.
People use dogbones all the time to allow plugging 30A cords on a 50A service, and the risk of doing so is minimal. Just make sure you protect the power cord so you don't inadvertently drive over it or otherwise damage it.
The only thing that works on a RV is the owner...