Why would a 32 foot 5th wheel be any shorter than a 32 foot conventional trailer? 32 feet is 32 feet regardless what is being measured.
For what it's worth, I have only been asked to leave a perfectly good site into which I fit EASILY due to a length rule and that was at Mount Rainier national park (federal campground). Their reasoning in that case was that it would be impossible to maneuver through their campground (to where I was set up) with a trailer longer than 28 feet. It was just as easy getting out as it was getting in.