So I am currently working through this adventure too. Just called the SC to see if they would order me the four ambient light strips. Funny thing - I have a 2013 S85 and although I don't have the physical lights installed in the car, I have always had the 'ambient light' button in the MCU (it never did anything obviously). My car was made back in the days where 'Tech Package' was a thing, which my car has. I wonder if they just pushed it out in the software to all old S's at one point.
I feel like my car was a bit of a mutt (transition car). I have the tech package and parking sensors, but no folding mirrors. The mirrors are heated and auto-dimming though... hah. I was missing some lighting in the doors and the trunk (which I added).
Looking forward to getting this nice feature for the interior of my car.