This part of the procedure (bringing the cabin alt to 0) always sounded wrong to me. Unfortunately, I currently do not fly A320, so I cannot check how the cabin altimeter works. In my aircraft (which is similar to A-320) it shows altitude in the cabin, based on pressure 1013hpa (29.92). So if you land on the airfield with RW elevation = 3000', with QNH=1013Hpa and open doors, you will see Cabin Alt = 3000'. If QNH is lower or higher than standard, then Cabin Alt will be higher or lower (based on 27.3' per 1Hpa). May I ask somebody, who is flying A-320 to check, if it is the same for Airbus?
If the principle is the same for A320, then think twice when you bring your Cabin Alt to 0, in preparation for landing on high altitude airfield - you will probably get Very uncomfortable Cabin V/S, when you fully open your outflow valve on final.