In my airline, we cant go below green dot, F or S speed without selecting the next stage of flap, having said that we only mandated it around two years ago in company procedures. Before this guys would apply common sense and not normally go below it anyway.
As pilots we become so used to following everything to the letter of the law, when a law is not written we are often at sea wondering what to do, then someone messes up and....hey presto, there is a new procedure and, if your company is like mine, it takes a few weeks to find out why, then the rumours start.
I believe that Airbus has not specified a restriction on selecting a speed on approach below the manoeuvring speeds because they, unlike modern Airline management allowed some PIC discretion to fly the aircraft they way the PIC thinks it should be flow within the normal envelope.
Our reactive airline safety departments however remove all discretion, I sometimes wonder if I should be retitled pilot under command (of airline management) rather than pilot in command.
Whinge complete, you have the comms.