Towing Capacities

I apologise to one & all if this is going over old ground but I did a search & unable to find a thread on the topic of towing capacity. As I understand it the towing capacity of your 4WD or non 4WD comes down to the basic specifications. The rule of 10% of the towed object doesn't apply. Vehicles that are rated by the manufacturer at 3 tonne or 3.5 tonne towing capacity is basically smoke & mirrors what should be asked by the purchaser is "What is the manufactures specifications for tow ball weight?" When the answer is 180KG!! One should ask why then, is the vehicle advertised by the manufacturer at a legal towing rate of three tonne but the tow ball weight allowed is 180kg a lot less than the 10% rule!!! I think some vehicles like the Patrol are rated by Nissan to tow 3.5 tonne. What is the tow ball weight is it 250KG? I believe the motoring public maybe misinformed by vehicle manufacturers. It is awfully hard when trying to purchase a vehicle & the dealers don't know what it's all about,they just go on what is printed in the specs from the manufacturer. Find tow ball weight on a brochure? It is not until you purchase the vehicle & start reading the owners handbook that this subject is covered....too late she cried. I think there might be people out there that have a van & towing a heavy van illegally & what happens when disaster strikes? If an insurance assessor is half switched on he/she will look at the vehicles capabilities & the specs on the van & we could be in trouble especially when manufacturers of Vans are sometimes understating the actual weight of their product!! It would be horrendous if someone did have a prang (Vehicle $70,000 & Van 60,000 total $130,000) & find out you have exceeded the manufacturers specifications & you are therefore not covered on your policy!!!