our 06 cedar creek came with the same warning
its not as much to do with the fithwheel hitch areas, as it is with the rear of the rv frame being strong enough to withstand the loads a trailer and added tongue weight would apply.
weight reductions, thinner frames, etc that allow a smaller tow vehicle also limit what can be added out back
few do make them with hitch for 3500lbs or less
as far as a heavier you may have to have it engineered.
that being said
i see em all the time pulling a tandem axle trailer loaded with toys behind a fiver
USN Retired, Life time member of the DAV.
Enjoying the 2008 Damon Tuscany 4056, no your eyes are fine, there are 6 slides