I just read this, and not having a FCOM, I wonder if Airbus is trying to make one procedure for all small Airbusses.
Remember that on the A319 and A320 the centre tank pumps feed the engines. On the A321 they feed the wing tanks.
So maybe you wait for 3 tonnes, so that when you turn the pumps back on there is room in an A321 wing tank (no inners and outers on an A321!) to take the fuel?, and the A320 drill is kept the same?