Spoiler response V Aileron response
I fly the A320 and always use Conf 3 rather than Conf Full in gusty/crosswind conditions, primarily for better controllability.
From what what I have read, Conf Full on Airbus uses a lot of spoiler deflection for roll control, and the response of spoiler deflection is not linear ( unlike aileron deflection ) leading to overcontrolling and PIO.
For myself, Conf 3 with more "normal" aileron response makes the 320 fly like my previous non-FBW types, and makes the gust corrections much easier.
I am not a test pilot, so if another explanation is correct, I would be happy to stand corrected.