I know the same switch will keep a MD-11 at a slight pre-press when pushed.
Approx 250 ft below ambient if memory serves me correctly.
This to keep doorseals and the like positively seated during the ditching itsself.
Does it do the same for an Airbus?
Keeping the fuselage slightly pressurized will also add a degree of stiffness, increasing the fuselage's rigitity.
Although I am unsure how much is to be gained from so slight a pressure.