the young pitlane guy the bbc have said at the end of the qualifying that the flexible diffusers on the toyota had been deamed illegal instead of saying the flexible wings
It's the horizontal planes on the rear wing, NOT the lower diffuser. There's not much benefit to a flexible lower rear diffuser. It's purely a safety regulation to prevent dramatic failure as if they broke at high speed the car could get punted into the wall with little warning, or bits could hit a following car.