I am aware of the subtle change in weight. China does prefer to trade their commodities in metric units rather than the western imperial system.
This gift validates your business relationship with dealer.
I have a good business relationship with my coin dealer who will give me at least 10% of the price tag of about anything numismatic in his shop and pretty good low premium above spot on bullion from now on.
It pays to find a good dealer and stay loyal to them. More or less.