It is staggering the misinformation that is out there.
You can tow a 5th wheeler on a car licence if the GVM is under 4500kg. You can actually tow a trailer up to 9000kg on a car licence, although you will be hard pressed to find one and keep it within all the weight limits.
It makes no difference where the hitch point is. It can be in front of, over and even behind the rear axle, you don't need a truck licence if the GVM of the tow rig is under 4500kg. There is no ADR regulation for the positioning of a tow hitch in front of or behind the rear axle.