From A320 Instructor Support Manual- ' You may fly below current maneuvring speed of the current configuration, provided you fly above VLS '.
Of course you can fly below S speed with Flap One out!
What do you do in case of a flapless or slatless approach, reference maneuvring speed? You fly below your maneuvring speed but > VLS.
But when you are told to fly 180kts by ATC, for example, and S speed is 185kts, most punters will happily fly high drag with flap 2.
Personally, I don't do it. The concept is poorly understood by A320 pilots. And seeing an aviator turning blue, because you are a few knots below S speed, ain't worth the hassle!