I was always under the impression that one advantage of specialist camping tyres as opposed to similar van tyres is that they are designed with the typical motorhome's usage in mind. Many motorhomes do not do a large mileage but it stands to reason that the lower your mileage the more the 'van is standing on the tyre, possibly for long periods. So proper camping tyres have side walls designed with this is mind. There is no doubt that you can buy non-camping tyres with the same load specification, which on paper appear to be the same as camping tyres, but are they the same and how will they be affected by bearing all that weight for several weeks without being moved?
Personally, if there's the slightest doubt I'm going for the proper job. Even if If you save £200 by buying a set of non-camping tyres, when you average that over what may be a seven-year period, I am not taking the slightest chance with what I consider the most important part of my 'van (after the brakes possibly!) for less than £30 a year. And if the cheaper tyres aren't as good and don't last as long then ultimately they could end up being more expensive.
So yes, every one's entitles to buy whatever tyres makes them happy, but my advice would be that this is the last area of your vehicle on which to be sawing the last ha'penny in half.