If the internal water system from tank to faucet is within an exterior climate isolated area, you probably would have absolutely no worry about freezing.
If you have an external heated hose connected to the city water bid and to your RV, you have the potential of freezing at the bid or trailer connection.
So you can do what you know probably wont be an issue or take a chance on what could be an issue. Your call.
In freezing temperatures, I use the internal system. I use the external only to top off the internal thus reducing any chances of a problem.