"Same CI cannot work on there and back sectors unless there is no wind."
Not so sure about that one, at least on the ship I fly. The FMC takes actual wind into account, speeds up for a head wind, slows down with a tail wind. Thats the concept, a ratio of fixed costs and variable costs ie crew,lease,maintenence etc and fuel. Wind is accounted for and speed adjusted in real time by the FMC.
While it may seem a blunt tool that seems to work on some sectors and not on others, its an across the fleet philosophy. If it was left to the pilots to program what their best theory is then who knows what would happen. Its an average percentile saving that is being sought!