Are you saying you have Two 30A MALE plugs that combine into One 5a FEMALE plug???
I've seen 50A Male to Two 30A Female.
Allows plugging into a 50A power receptacle and then 2 30A cords being plugged into adapter (powering 2 different rvs)

There is a Double 30A Male to a a 50A adapter with a 30A to 20A adapter.
Idea is one 30A plugs into 30A power receptacle and the other 30A plugs into the 20A receptacle on your sites power pedestal.

But guess if you are paying for both 30A sites then you can just plug into the 30A receptacles
Not sure how the 50A Surge protector will look at both hot legs from same source---the 30A receptacles are probably being fed from same hot leg in CG electric system (50A being feed from 2 different hot legs)