Cabin Crew here.
As far as I am aware, the decompression happened during or immediately after the meal service, meaning 365 would have had their layups. I agree that the crew were most likely clearing in those lay ups.
Personally, I would have gone through with our big garbage bags, and just chucked it all in, EasyJet style. I think we could clear in a 744 in about 10 minutes that way.
Following the descent, it may have been considerable time before landing into MNL. I presume the a/c also flies at slower speed at 10,000. Another theory is they were serving juice or water. Keeping the crew busy during an emergency is very important as it helps us remain calm and therefore more able to calm and reassure the pax. Not sure I'd do it on a cart though.
Congrats to all the crew, my thoughts are with all my friends who fly for the Q!