Graphite Watch and Graphite Milanese are PVD coated to prevent color from rubbing off and they can damage each other.
The Space Black is DLC coated and so was the Space Black Milanese loop and those could also scratch each other. This has been known since the Space Black Watch and matching Milanese were released back on the S3.
Raw SS micro scratches can be polished PVD/DLC cannot. Sapphire can scratch Sapphire. Diamond can scratch Diamond. Materials of the same hardness can scratch each other.
Have no fear, next update brings the swipe option back as an option.