Fisher Bill - I don't know if the Campgrounds would have much of an understanding of the subtle differences between backing a 5er and backing a TT. But I do however believe they would understand an irate camper standing in their office all pissed off because he couldn't back his fifth wheel into a particular site because, a couple of tree are situated in a particular bad spot, the electric post was in to close to a couple of huge rocks, or whatever. An irate customer is what the campground would long remember and make sure not to put a 36-foot fifth wheel on that site again. If the campground says it won't fit, I would tend to agree with the guy that knows about his own campground.
Everyone says they can put a 36-foot fifth wheel on the same site a 30-foot TT will fit. But then, they can's see the trees, bushes, elec post, water spigot, drop off across the road, telephone pole, low wire, slope on the site, or anything else that can effect what can go where.