The B737 has a similar statement in its manual allowing you to operate with a thin layer of ice/frost within an outlined area marked on the wing.
737NG has the black markings. Boeing say its ok with Ice the CAA/FAA say clean wing. Unless something has changed recently.
Something to do with A330 outer tank ice...?
I believe Airbus was doing some work on this in recent years
No need, just open the fuel transfer valves before refuelling, the cold fuel drains into the main tanks and the new warm fuel fills the outer tank, defrosting the wing. As long as you remember to close the transfer valves or the fuel won't go on.
Assuming the fuel from the bowser is above 0 deg of course.
