Two other problems. One, the pedestal is likely not wired with both legs of the electrical service. This means that any energy management system in your rv will only see 120 volts when it measures the voltage across the two lines that feed the distribution system. The management system's programming then act as if the system is connected to a 30 amp service and will run all your electrical systems accordingly. Then there is also a very good possibility that the 30 amp breaker and the 20 amp breaker are either tied together or the pedestal is wired back to the distribution panel and is protected by a 30 amp breaker there as well as at the pedestal. So even if neither breaker in the box is tripped, you may very well trip a breaker at the distribution panel, and you probably don't have access to that breaker to turn it back on.
Those cheaters are generally not very useful.