Sorry to contradict, but that is incorrect. Standard RV 50A service is 240v and exactly the same as a dryer or stove outlet. Both 120v and 240v are available with that type of electrical service. Yes, the load center (breaker box) in a 50A RV has two separate bus bars, but so does standard residential electric service. Each branch circuit can get either 120v or 240v, depending on the breaker type selected.
There are RVs that have one of more 240v appliances - that has become increasingly common in higher end "all-electric" models and may be used to power 240v clothes dryers or inductive cooktops.