Trnsl8r
S85 2012-2018, X90 since 2016, 3 since 2018
Actually it does, you just can't see it. The folding mechanism is very clever. The hinge is about halfway down the stalk and the mirror shell pivots in.
Check out this video clip from another thread:
Model S in two showrooms this coming weekend
About half way through, after the car clears the doors, you'll see an employee fold out the mirrors.