E92LNGCGY, I've noticed the same thing on my AW car... I thought WTF??
Anyway, I noticed the same pin-prick like rust mark on the rear bumper cover and realised it must be some contaminant stuck to the surface.
I've never used a clay bar but this spring I might give it a go.
If you've seen the production videos the car is basically electroplated with the primer so I don't think the marks are rust from beneath.
2013, AW, xDrive35i, M Sport Package
, Technology Package
, Dynamic Comfort Package
, Premium Package
, 3M Clear Bra, Euro foglight switch, a few coded fixes