I think the only ones that would be exempt are the RV drivers, just cause a guy lives on a farm doesn't mean the enforcement people are gonna accept that he should be exempt when they stop him pulling a pc of heavy construction equipment and he tells them it's for farming. It may very well be true. not sure who the burden of proof would be on.
I don't think the average F-350 owner is gonna be a CDL holder, or is even thinking about one, when he plans on pulling a 20,000 pound stock trailer 200 miles to the state fair. So the truck may be legally capable but many/most of the drivers wont be IMO.
JB.