Yes, the 80 series I drive (and am working on a EPA-illegal turbo 1HZ conversion for) was rated for 3500kg (7700lbs) everywhere except the US where it was only rated for 5000lbs (2260kg). And they make you (or the dealer back in the day) install an aftermarket tow bar instead of using the factory crossmember. Totally arbitrary nonsense, nothing to do with safety or mechanical capabilities.
The only saving grace here is (a) the EPA doesn't actually enforce rules against diesel swaps, and most states tolerate it--some will even give you a new VIN! (b) nobody (law enforcement) cares about GVWR unless you're operating commercially or doing something obviously unhinged.