And:
"But the attention is on Mercedes at the moment, not least because they did not run the new passive F Duct system which has been cleared by the FIA’s Charlie Whiting. Perhaps we will see it on the car tomorrow. It’s a powerful tool, but its benefit will not be seen here. Malaysia and especially China with its long straight will really show the benefit." - James allan
maybe they decided to take the new ducted wings off the car for the reason that they might only have one each or something..especially since it was quite tricky in the wet. but this boasts well if you ask me...since there is obviously an "X-amount" of time in the pocket due to an invention that wasnt even present on the car today.