[Tannaton]

I don’t think anyone would disagree in principle with that - but even left in D the gearbox will work out and select a suitable gear for the terrain, weight and commanded throttle. You will get a faster responses to increases in gradient whilst in S but the price of that will be increased fuel consumption overall.

What the manual is telling you is not to use geartronic to hold the gearbox in too high a gear for the conditions.