Well come on, this is just too weird, we have to get to the bottom of this somehow. I also have EXCATLY the same mark in exactly the same place on the top of the steering wheel in my 67 plate Mk 7.5 GTI 230 (I had a 14 plate Mk 7 GTD before the GTI and that definitely did NOT have this imperfection on top of the steering wheel).
I had completely assumed that I was just unlucky in having this mark/blemish right in front of my eyes (the rest of the car was spotless when I took delivery) but it clearly must be an actual manufacturing issue.
Very strange...