Quote Originally Posted by Euclid440 View Post
What you are seeing may be what Alex is talking about, and the very edge may be microscopically convexed, and when put on a hard flat stone the edge is not making contact, and the back of the bevel is polished.

Or could be hydro-planning also. Hard to say, either way, the edge is not in contact with the stone.
Was done on a 'test' kana blade. The edge was untouched so I'd suspect hydro-planing.