Adding speed due to incorrect VAPP calculations in the FMS I understand. Adding a few knots in order to lower pitch attitude in config 3 also makes sense to me.
But primarily I see the addition of 2 knots (and it's almost exactly that amount) due to gusty conditions even in VREF is correctly calculated. Firstly an Airbus has GS mini function which takes care of ensuring that a margin is added when there is a headwind on approach higher than that expected on touch down, so that you don't get caught out with the wind drop. Secondly VLS is an Airbus systems speed. It is not a structural or aerodynamic speed. Going a bit under VLS is not the same as going below green dot at high altitudes. And even if you do, at lower levels all commercial Aircraft with all engines running have plenty of power to get themselves out of the back end of the curve, and so dropping a couple of knots into VLS has no real meaning except frightening some pilots.
All your really doing by adding two knots is to increase your margin vs stall speed. But will 2 knots save your life? Are pilots getting a bit too paranoid here?