The things that would primarily affect towing capacity are the chassis rating, rear suspension load rating and braking capacity. As far as I knew, the chassis on the utes went almost to the rear of the tub, and the hitches bolt onto the chassis anyway.
There IS a significant torsional load on the ute, the distance from towball to axle on the Navara would be greater than that on the Patrol, so there might be something in that as well, but I wouldn't put it past the RTA etc to miss that point. They probably consider any mass behind the cabin to be "over the rear axle" and that's good enough.
In a way, it's kinda dangerous, but it's also kinda simple. I'm not saying that simple is dangerous, I wouldn't mock politicians like that.
There IS a significant torsional load on the ute, the distance from towball to axle on the Navara would be greater than that on the Patrol, so there might be something in that as well, but I wouldn't put it past the RTA etc to miss that point. They probably consider any mass behind the cabin to be "over the rear axle" and that's good enough.
In a way, it's kinda dangerous, but it's also kinda simple. I'm not saying that simple is dangerous, I wouldn't mock politicians like that.