Mmmm
Just spoke to a guy who had the ZFW drop just under 9T going to the west coast of the US, did the correction to the trip fuel/total fuel double check by requesting a new flight pan.
MAND went up 500kg!
New plan showed they were now 1.3T below the legal departure fuel based on their LNDG CORR.
Perhaps CX should say ZFW changes up to "X amount" are acceptable.