Surely for Performance A aircraft the defined Vref for the approach (which may have an increment added to establish a Vapp speed) would only ever apply down to the screen height of 50ft.The Vapp speed for the A320 already includes an increment for the autothrust which doesn't apply for manual thrust approaches. This increment (when applied) is allowed for in the performance calculation for landing distance. In practice we rarely choose to fly Vref at the screen height when manual thrust flyiing.
An over fixation of maintaining speed (Vapp or Vref) below the screen height isn't in keeping with the requirements of a Perf A aircraft.
The certification of the aircraft would include a consideration of the speed/handling characteristics of the aircraft throughout the range of conditions likely to be encountered and would as such influence the handling advice to pilots, in particular below the screen height. In the A320 series that advice is to prioritise attitude and sink rate during the flare and landing sequence and not speed. Both of these are "eyes out" tasks. If Vapp (or Vref) is not achieved at the screen height, or the aircraft is experiencing rapid changes of speed/thrust then the aircraft is potentially unstable and a go-around or baulked landing might be best considered.
I'm an average pilot on my best days. I have to say when conditions make speed control a challenge I don't rate my ability to control speed more accurately than the autothrust. Whilst I'm more than confident to do so when required I've never had that little confidence in the autothrust function.
Airbus have an extremely competent flight test team and certification process. Follow their advice. To formulate alternative practice on the cuff would seem risky.