Hi ChiefT,
It's not really uncommon for airlines throughout the world to have the MTOW certification "derated", CX did it with their B747 Classics near the end of their service.
It is done because airports charge their landing fees according to the MTOW at which the aircraft is certified, i.e. the lower the certified MTOW, the lower the landing fees, regardless of the actual AUW of the airplane.
Hope this helps,
Cheers