Some trailers come with a pintle ring because they are too. heavy to haul with the strongest standard ball and socket.
For some lighter bumper pulls offered as rentals, the equipment may come with a pintle ring because the market is one that usually hauls heavier equipment. But in the case of the car hauler, it is probably just too big for a class V ball. That means either gooseneck, or pintle, and pintle keeps going beyond the limits for gooseneck hitches and balls.