For the tires to swivel without hitting something, the mating to the dolly has to be from above, like a gooseneck trailer. Maybe this dolly lets a tractor tow a trailer of some type that doesn't normally hook up to a drawbar.
BTW: Aircraft tow dollies normally only have tires to support the dolly while it is moved into position by the tug. Once the towbar is hooked up, the tires are off the ground and the towbar is supported by the nosegear and the tug. Ken's dolly is made to support weight on the tires.