The radial lines in the counter sunk holes are from a counter-sink cutter with the correct angle for the bolts being used. I am a CNC machinist and this is how manufacturing produces those features. You will never get a perfectly smooth surface (cutter wear) or a perfect bolt circle (all machines have positioning tolerance). I believe that a sprotor can work because chain oil/wax flies off in a outward pattern unless you drench your chain with oil when it is sitting. Harley also proved that you can have a brake and sprocket connected, just look at old sportsters. They work just fine. Just my 2 cents.