Robbbyr posted links to some very good reading on the subject.

Some references:

The 50-amp 120/240-volt 3 pole 4

https://www.rvtechmag.com/electrical/chapter3.php
AC Electricity

You are correct that a 30 amp RV plug is going to give you 3600 watts of power. 30x120=3600

A 50 amp RV plug is going to give you 12000 watts of power.

L1 50 amp x 120 vac =6000 watts

L2 50 amp x 120 vac =6000 watts

Technically it is not 100 amp it is 50 amp twice.

Lets say I have my 50 amp trailer plugged into a 50 amp RV service.

My EMS reads

L1 120v 50amp

L2 120v 50amp

I'm using 6000 watts of power on L1 and 6000 watts of power on L2 for a total of 12000 watts.

If I take a clamp on amp meter and check the Black wire on L1 I will have 50amp. Put the meter on the Red L2 I will have 50amp.

Put the meter on the White Neutral I will have 0.

It is Alternating Current

I hope this helps.