Larry Williams
The matrix that mounts the diamonds is intentionally soft. Both the nickel and resin bonds are intended to wear away as the diamonds fracture along David's cleavage lines and spall away in use to expose fresh edges. This is how the life of the diamond stones or wheels have an extended life.

If you have a dry grinder try this. If you've done much grinding of steel you'll have some grinding swarf around your grinder. Pick some swarf up, pinch it between your thumb and index finger. It'll looks like it's a powder but it will lift in a clump. This is because it's actually tiny shavings. If you look closely the swarf looks line very fine steel wool.

Stones cut ferrous metals the same way, they make little shavings. Some of those shavings go around the diamonds but some are directed into the soft matrix. This undermines the diamonds quickly, much faster than when working material that generates a granular swarf which is what the diamond mounting system was designed for. Diamond wheels and stones were designed for things like carbides, stone, or glass. Using them on ferrous metals greatly shortens their life.

At least, this is how the tech rep for the company that makes the diamond wheels for the diamond grinder we have in our shop explained it to me. It's also why I follow the instructions found in most machinist texts and grind away the steel backing on brazed carbide tool bits before sharpening on the diamond grinder.

On edit: The tech rep's comments agree with my experience. A diamond stone lasts me a lot longer dressing oil stones than working tool steel.