Not sure how they categorize them. IN MN sport trailering is allowed with a fifth wheeler under 25' and towing an RV.
I was at my local Cummins store last week and we saw a Ford PSD go by pulling 2 fifth wheel trailers. Something along the line of this hitch dolly was on the rear bumper of the first trailer. It was not a pintle hook style used by the commercial trailers.
Horse trailers, too.
IMHO God gave some horse owner's as little brains as the horse they own.
diesel on
-John