I started flying 320's with a launch customer. X-W technique has been a poorly communicated evolution- like many things Airbus.
The FCOM's have been full of holes for years. Slowly, information has been inserted all over the place by Airbus.
I still get guys telling me you never need to drop a wing with Airbus because its fly by wire or the active flight control law in the flare is blah blah.
Anything above 10kts X-W I drop a wing for finesse. Above 30kts X-W its for directional control.
Been doing it for the last 12000 hours.
And funny enough, Airbus, after a few incidents, has got around to scientifically expressing what good pilots have been capable of doing for years ( in the link I pasted ).