Consider that an A321, or any modern Airbus for that matter, could easily be 10 kts faster over the threshold given a strong headwind (GS Mini). Are we therefore to say that whenever the approach speed is higher than normal that we ought to reconsider the approach category? I don't know the answer but somewhere in all of this will be an argument for keeping things consistent despite the occasional deviation. Flap3, though nice to perform given a long runway, is not considered by Airbus as "normal".