I doubt having it in sport mode would make much of a difference, as it alters throttle response by tigting up pedal travel and I don’t believe he Megane has true active suspension if any. That said KF shoud not have been altering customers settings and certainly not taking it for a boy racer test drive!
The question is, would you be happy for XL rated tyres on the fronts, when the car wasn’t designed to use them or do you push for matching standard set or at least a replacement to match the existing tyre on the opposite corner!