Well, that's actually not true. The CNY is defined in "Part 1, Conditions of Service" of the standard contract and has no voluntary or ex-gratia clause attached to it. It is simply payable, that's it.
The flying staff manual is available on the DPA website. There also seems to be confusion on the FLPS (fixed leave period scheme) only applying to B scale by COS, whereas in reality the FLPS applies to all KA pilots but the amount of leave days one is entitled to is defined in the respective COS. In my case that is 42 and stays that way, on the B scale that climbs to an eventual 48 days.
I was referring to the fact that we don't get any ex-gratia payment by definition. Everything we get paid is contractual, whereas at CX there exists such a thing as a discretionary bonus.