[Snoking]

Circuit breakers are there for more than a single reason, along with electrical codes. Yes the 30 Amp main breaker in the power center will protect from overloads within the unit down stream of the panel. It will not protect one from a problem up stream of the power center that is supplied with wiring rated for 30amps and is feed from a 50amp supply.

In life beyound RVs this would be a code violation. Example would be a sub panel in your garage wired with #10 wire from a 50amp breaker in main panel. Red tag, failed inspection.

People just need to be aware of the risk no matter how small, as their lives could depend on it. Example could be a loose connection on a lead comimg in to the trailer at the inlet or panel that created enough heat to melt to insulation on the wires and allow a short to occur.