Yeah, it's a joke. The clock face comes in white or black depending on your choice of S or non-S.

If you choose black dials for your S you'll probably get a white clock; even though the black dials are options on the S and stock on the non-s and the non-s comes with a black clock face.

IOW, even if you choose black dials option for your S you'll probably still get the white clock face which is standard on the S.