I think most CX crews preferred serving the second meal mid-flight, as they prefer to arranging their rest period in that method.
The first set of crews would just have came out from their resting period and changed back to uniform or did a quick clean up. The second crew would then serve the meal together and then go to rest. Maybe less congestions in the bathrooms mid-flight. Anyway, I think most CX crews really like that style of rest period.

It is also dinner time at the origin so crews think that they will have less work to do if they serve the second meal mid-flight. However the pre-arrival meals are so "tiny" now that if it is just hard not to order a snack prior to arrival. Most Hong Kong folks also tend to stay up late too so they will request a third meal anyway. At the same time, I presume heating up a burger or preparing a noodle soup is easier than preparing a full meal.

Carfield