Surprise, there are inconsistencies in the osm wiki.
This one makes more sense to me
"The caravan might be a trailer towed by another vehicle (ie travel trailer, camping trailer, popup camper), or a larger motorized vehicle (recreational vehicle (RV) or motorhome). "
which is from: Key:caravans - OpenStreetMap Wiki
I think we would find that ‘caravan’ is used in the wider sense most of the time

I would tag it as:
caravan=yes
motorhome=yes
trailer=no
maxlength= *