That isn't logical, since the same hitch is used for the 30 (3.0), the diesel, and the 50, and they have different tow ratings between the various models in Europe. The hitch may have a higher capacity, but then the question is why the 30 has a reduced published capacity (perhaps the smaller transmission)

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue