It’s just to help reduce the chances of a secondary stall during the recovery. The problem is, if you read the QRH, you don’t select flap 1 until after the recovery. You have to look a little deeper into the FCTM, as you have, to discover what Airbus actually want.
there’s a very good video on AirbusWIN about stalling. Well worth a watch.
Also, if you can talk your trainer in to showing you “deterrent buffet” in the sim with the motion on, that’s a real eye opener! How the hell the pilots of AF447 rode that out I will never know!