Auto Dim Rear View Mirror.

CJ, you will only notice it as the mirror doesn't dip, the brilliant lights behind appear green tinted when it the system is working.
TBH I think if you have privacy glass the auto dipping is hardly noticeable - usually only when some twat with aftermarket whiter than white lamps with poor alignment is behind you, but those idiots also often drive so close you cannot seen the lights anyway at night! What I think is really cheap is that if you have the auto dipping RVM you don't also get dipping wing mirrors and they can often be more annoying than the rear view mirror. I haven't yet owned an RR that has auto dipping RVM and wing mirrors, it hasn't even been an option to have dipping wing mirrors.

I think the larger area of the door mirrors would make it prohibitively expensive.

According to the LR website explore section the power folding memory door mirrors (standard on dynamic & prestige option for pure) do dim? Is this not correct then?

"Exterior Mirrors – power-folding with memory function

These advanced, heated mirrors come with ‘auto dimming’ which detects excessive light and glare then automatically darkens the mirror glass to improve vision. They are also power-folding to avoid damage when parking in confined spaces and 'auto dipping' in reverse gear. Downward lighting ‘puddle’ lamps project an illuminated Range Rover graphic on the ground, to light your way.

The mirrors are also equipped with a memory function. Once you set your ideal seating and mirror positions, it automatically recalls your preferred driving position settings."

I haven't noticed them dipping, LR website is notorious for it's inaccuracy though

The wing mirrors dip when reversing, an option selected from the system settings on the steering wheel. The interior reverse mirror dims, but does not dip