There are a lot of personal definitions coming out here.
S speed is the manoeuvring speed at F1 (not config 1 as per take off accel!).
Deliberately flying below manoeuvring speed is poor airmanship (even if VLS/ATHR is there as a back up to look after you!).
You may be planning a straight course, speed reduction but sometimes you have to unexpectedly manoeuvre..................................hence manoeuvre speed!
This is nothing to do with France or indeed the Airbus but is valid for every tye I have flown (more than a few!).