OK I called my local BMW parts department and they were nice enough to pull a rotor from stock and take a look. The area that I mentioned in my last post turn out to be rivets.
While I have seen aftermarket with rivets on the horizontal plane to the rotor surface, these are on the hub, which is vertical plane to the rotor. I thought maybe part of a sensing circuit for rotation etc..
The BMW parts person stated that the BMW stock rotor has a aluminum hub riveted to a cast rotor and that is what they are.
This means the Centric are 100% cast and require no rivets. I am going to do the brakes Sat. so I will give some feedback.