Sounds like they are gun shy and want to provide legal documentation releasing themselves from any implied or legislated responsibility to the buyer in regard to the serviceability, cosmetics, or functionality of any part of the RV....
Probably been sued at least once by some customer that wasn't satisfied with the outcome of a warranty issue from the manufacturer and the customer took it out on the dealer...
Doesn't mean they won't warranty any work they perform, just that they won't be held legally responsible for the workmanship of others...