I don't have an X5M owner's manual to check. The E70 was rated 6000 lbs. Edmunds has reported that the X5M tow rating was increased to 6600 lbs.

Where was it reportedly to be reduced?

__________________
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