It's a simple warning in approach about falling speed. Some thing like verbal trend arrow. Apart from WS the reason is flight path or thrust if in manual thrust. The practice of moving the thrust levers out of CLB towards MCT if taken too far has the potential(actually I am sure it has happened) of triggering GA mode which will effectively end the approach. So through the FC Bulletin which I mentioned it was stopped and complete switching to manual thrust was recommended. Either the the earlier or the later recommendation doesn't seem to exist in Airbus new manuals. So if a company manual has it then it will be a good idea to get Airbus position on the matter under tech request.