Here is two scenarios I have run into. Scenario 1: when booking reservations at Lake San Antonio Ca for thanksgiving, I noticed the 5 sites I wanted showed they were without power. I booked the next 5 sites and checked periodically to see if they had fixed the power as I wanted those sites. Never fixed. When we were camping I waved down the campground host and asked what was the holdup in repairing the problem. It had been 5 months. He said there was an issue in the wiring feeding those sites and no-one has figured out what to do. Obviously this campground is wired in a daisy chain fashion with 5 site per circuit.
Scenario 2: 2 buddies and I were camping at Pinnacles National Park out side of King City, Ca . We were doing diner at 1 trailer in 100 degree heat so the AC was going plus other items and out goes the power. I went next door and checked mine and it was working. Checked the other side and his was working. #0 amp was not tripped. Waved down the campground host and he said hold on. Back he came and said you should be good to go, which we were. He said the breaker in the main is weak so he just reset it. Asked him why he doesn't replace the breaker and he said he has reported it to the electrician. In this case, each site is a home run to the main panel
Got off track there.
I am guessing that a power pedestal that has a 30 amp and a 20 amp outlet has both breakers connected to a buss bar which is serviced by a 30 amp main. If was serviced by a 50 amp main then I would be fine utilizing both outlets but that seems to be unlikely. A peak into the main would answer the question..
Edit: I think I was typing while others were posting. Thanks for the input.