The only time you should need to "pump" the pedals is if the pistons have been forced back into the calipers. How you could do this in an a/c I have no idea, but it is often an issue with motorbikes that have suffered a "tank slapper".
However, on my pre-landing checks, I always pump the pedals to ensure that there is brake pressure when you need it. The last thing you want is to apply the brakes and have nothing happen, especially on a short runway...... If the pedals are soft during the pre landing check, then at least you have time to make a decision rather than when the boundary fence is coming up at you at a rate of knots.