Machinbird
You seem to be in the possession of inside information regarding the arrangement of the 'bus control system, however how certain are we that the bus EFCS in Alt2 does not have authority to "center the ball" in Alt2, and only sends a signal to the PFD equivalent of the ball telling the crew to center the ball.
Sorry, I don't have any inside information, but I do have a downloaded copy of an A330 FCOM which states that for Yaw control in Alternate 2:
Dutch roll damping is provided with authority limited to 4 deg in CONF 0, 15 deg in other configurations.
Turn coordination is provided except in CONF 0
So for the AF447 case the EFCS does not centre the ball, although in most other cases if does.