I have seen this twice this summer.
Recently at the KOA in Cleveland, TN -- hubby was in the area for a couple of weeks for work -- he brought the camper with him but stayed in a hotel during the week -- that weekend I came to TN Thursday Evening about 6:00 (from KY) to spend the weekend--earlier that day Hubby took the camper to the KOA on his lunch break (around Noon)and asked if he could set-up and leave to come back in a few hours -- they were not busy at all -- no one on the site we were going to. They told him it was $10 for early check in. He just paid it -- set-up and went back to work for a few hours.
Also saw this at Jelly Stone CG in Nashville this past May.