Thanks, Orange future,
If they are trying to avoid the (roughly) +8 pitch using Flaps 1 (slats only) at "S" speed, it seems to me there are two better options than extending the flaps:
(1) fly faster than "S" speed;
(2) request a slightly higher holding speed than the normal prescribed limit to enable them to stay clean.
I would prefer (2). In my DC-10 days, we often used to ask for a higher holding speed to avoid slat extension, and it was rarely refused. As PENKO says, extending high-lift devices earlier than necessary is not a good idea in icing conditions.