FYI, I carry a 50 to 30 reducer and also a 30 to 15 reducer in which I have one of those multi-LED power correctness indicators.
First thing at a CG with 30A service is to plug the 30A connector in with the correctness incdicator. If all the lights come on to indicate it's OK, we're good to plug in.
At a 50A only campsite, I plug in my 50-to-30 adapter then plug in the 30-to-15 with the LED telltales. Only if they say OK do I then plug in my rig's 30A power cord through the 50-to-30 adapter.
In a season and a half, we've found a few prioblems, which the CG owners were relieved to find and soon fixed. We haven't had an electrical problem with any site pedestals this yesr, but it doesn't hurt to be very careful.
Frank and Eileen
No longer RVers or FR owners