Lots of scary information here!
If you have 50 amp service, you have 4 wires.
L1 - 120v
L2 - 120v
N - Neutral
G - Ground
With a meter, L1 to Neutral is 120v. L2 to Neutral is 120v. L1 to L2 is 240v.
Most current RVs with 50 amp service do not have any 240v appliances so there are no normal L1/L2 connections inside the RV like you would have in a house for air conditioning, clothes dryer, range, etc.
30 amp service at the pedestal has only L1, Neutral and Ground. If you use a 30 amp adapter to attach to 30 amp service, it combines the RV L1 and L2 circuits into a single circuit so all the RV circuits will be live. If you exceed 30 amps total current draw, the 30 amp breaker on the pedestal will trip.