I was surprised when I saw what held your typical US gooseneck with a huge trailer to the back of a pickup!There’s an odd (to me!) hybrid I’ve seen on American pickups where the gooseneck goes onto a ball let into the bed. Maybe that’s why?
The iveco I posted earlier is a proper mini artic with kingpin and rubbing plate etc, but the goosenecks I’ve seen on the tube often have the ball arrangement I just described.