Interesting observation.
AC stands for Auto Carriers. Their background was in commercial/industrial transportation. (I have driven an AC rail-car powered by two Gardner engines - in Essex!). They might well have registered the tow vehicle as a Tractor or Locomotive. It could then pull pretty much what it liked, and more than one of them. The top speed would be little less than the car version, but geared down for ease of carrying a load, none the less. In the same class as a Scamell Scarab. They would not be short of qualified drivers.
Mmm, is a Mini Comtesse a 5 wheeler, or a 3 wheeler. I'm off to go an tow armoured cars. Needle nardle noo.