I agree with the pull me over mentality if I’m wrong. One of the WA truck scales near Spokane goes off no matter if it’s an RV/rental truck, etc. It seems to have a weight/height trigger.
I drove over a couple of times in two different sized Uhaul trucks, and it still went off. Of course, it’s not required to stop with a rental truck for personal use. Nobody chased me down. Not that it would have been hard since I was just going the 60 mph speed limit. :D
I’m not sure why you think a TC can be an RV or cargo based on only the licensing. In MT, there is no license for TCs, trailers are generally permanently licensed, and so are motorcycles/atv/utvs. That doesn’t change what they are.