True, but that only protects your devices and your converter. Keeps your converter from being over loaded. You do not have 30A protection between the hot side of the converter and the main electrical panel. Don't assume cords, adapters or 50A plugs won't fail.
This is why the dongles have the warning that it requires a 30A breaker!! You wouldn't but a 20A breaker to replace a 15A breaker at home would you? No, because your residential 14/3 wiring is only rated for 15A. You need 12/3 for 20A.
You are plugging in a cord that is rated for 125V/30A into plug rated for 125/250V/50A. Everything works great till the 50A plug or the dongle fails. I seen happen to 2 RVs at the same resort. Ended up both RVs needed new converters and microwaves.