In the dim and distant past, the recommendation was to de-ice and/or anti-ice with flaps retracted and deploy them at the holding point when cleared for departure.
One of the reasons quoted was the ground engineers "didn't like it as the fluids removed the lubricant off the screwjacks" and also such an accretion of Type X on the flap mechanism may freeze at cruise temps and cause restriction when trying to deploy for landing.
But that was then, when men were men and had sheep for breakfast........................
