Originally Posted by
enzino
You may find your answer in the G+B dual hydraulic abormal procedure where it says to extend the landing gear at 200 knots to have better pitch authority in direct law with the remaining elevator and no slats.
Just a hunch.
But with all hydraulics working and the slats jammed (WTB on) you’d still have both elevators.
It could be as simple as Airbus only flight tested it in config 3. Does it really matter? Do what the PRO-ABN says and leave the whys and wherefores to the test pilots.