Going to HK last weekend and coming back from SIN last night I noticed that these seats (row nearest cockpit on 747 upper deck) were empty when we took and landed, but mysteriously acquired occupants in the middle of the night.

Does anyone know if these seats are now assigned for crew rest (like row 80 on CX). Does this happen on every flight where a relief crew is needed...or only if the seats are not needed for revenue?

I really can't recall 60AB being used like this before.