I think it's a recent USA/elsewhere thing, in that cars destined for the USA still have the forth button, but the rest of the world just has the lock, unlock and boot buttons. With sfax having a relatively early build, this expalins why he has the diamond button.
On my car, which is an August 2012 build, I have comfort access, powered bootlid, folding mirrors and xenons, and I have the 3 buttons mentioned above.
2012 BMW X3 20d M Sport Manual - Sapphire Black/Black Leather - Winter Pack, Access Pack, Xenons, Panoramic Roof, Professional Audio, 19" 369 wheels, Grad Tint Screen, Storage Pack, Sun Protection Glass, Electric Folding Mirrors. Oh yeah, and a 2013 Porsche 911 (991) C2S- Guards Red/Black Leather