Most places that have the rule, use it as a method to keep out trashed out rigs. When had a vintage Avion trailer, we had to send one a photo of the trailer. One place would not let us in unless we came in with a rally. We no longer recommend that park.
Honestly, for the run of the mill generic RVs, the RV campground owners and managers do not have a clue as to the year of an RV, unless they go out and look at the data plate to see when it was manufactured. We also had a 1995 Avion 5er that looked great. In 2005 it became a 1996 and in 2006 it became a 1997. No one ever questioned the information.
We have been parked next to a few RV snobs over the years. One time we pulled in next to a pretty new Monaco and as I was setting up my 1 year old Minnie Winnie class C, I spoke to him. He turned and walked off need clearance lamps on his nose it was so high in the air. later I heard him talking to another Monaco owner in his group and he referred to us a "Trailer Trash". Well, the feud was on. Out came 3 plastic pink flamingos and a flamingo "It is 5 O'clock somewhere" flag.
The calendar moves on and we had a larger and nicer 5th wheel and was talking to a Monaco neighbor. He was voicing his displeasure about an older GMC motorhome a couple of site down from us. I had spoken to the older couple and was shown the inside of the GMC. The older gentleman was a fantastic wood worker and had completely redone the interior. He has also gone through the driveline and running gear. Next project was a total repaint, but they wanted to get it out for some fun. If the exterior was going to be done to the level of work of the interior, it was going to be a show piece.
When we had the 1979 Silverstreak and the 1989 Avion which we had restored, people would stop and ask to see the interior. They could not believe the age of the trailers.
So if you run into a problem with a campground, move on down the road to a place that appreciates your business.
Ken