With a properly plated diamond stone using metal bond diamond crystals, which are the preferred type for this type of use, the diamond does not break down exposing new edges, it will sheer off at the bond line and be gone. With a less than perfect bond the diamond crystals will pull out. It is insanely hard to bond a metal to a diamond crystal, you have to use a reactive metal alloy in a minimum torr 10-4 vacuum chamber. When done right you can have a 25% bond line, 75% of the diamond crystal is fully exposed with no bond on it, and the diamond crystal will not pull out. With a properly plated diamond plate there is no bond taking some, or most, of the load when using it, all the bond is well below the abrasives. When you are grinding on a .01" wide bevel it would be very easy to overload the diamond crystals on such a small contact area. I think it is this, poor quality diamond, and inferior bonds that are what lead some people say diamonds are no good for sharpening steel knives, it has nothing to do with diamond itself.