No problem in flying below S speed by a few knots if required by ATC speed constraint. All in FCTM and FCOM. Poor understanding of systems by pilots coming from other manufacturers' types, not helped by poor (systems)training by both Airbus and airlines/TRTOs. As stated earlier, S speed is a target speed used by autoflight system with A/THR engaged using managed speed. Use selected speed and you can fly any speed right down to VLS. Of course, as you approach VLS, your protection above the stall reduces. Using flap and/or gear unnecessarily simply means you're burning fuel for no good reason. You can fly below S speed with Flap 1 (slats only) if you want to, but always best to respect your company's SOPs. If you're not happy with them, talk to your Chief Pilot! You can always ask ATC if 180/185 is OK and the required tolerance is +/- 10 kts.