Mark, this can be a tough discussion. A lot of it is based on our theory, guesses, hypothesis and personal experiences. Then the personal experiences are interpreted based again on theory, guesses, and hypothesis. Some of my knowledge has some scientific basis and a lot of it is just experiential with photographic observations of the results of using the abrasive mediums to sway my theories.
You grouped them into two broad groups, Diamonds VS Natural Stones. I really think there are at least three distinct groups: Diamonds and Synthetics Stones, the Natural Stones, and last the Ceramics. They are all, in general, as you wrote, abrasive mediums of basically hard particles suspended or held in place in or on a solid matrix.
The Diamond stones and Synthetic stones, IMO, are the most alike and most similarly rated or described. These are both man-made manufactured solids with known size abrasive material attached to the outside as is the case with diamond stones or mixed through-out the solid as in Synthetic Stones. With diamond stones the size of the diamonds and spacing determines the grit. With the Synthetic stones different hardness and size abrasive materials in a determined density determines the grit rating. The pointed or sharpness of the diamond particles removes steel as we sharpen knives by scratching it away, (machining as Tom put it) while cutting groves in the steel. As the diamonds wear, get knocked off and lose their points the diamond stone becomes less effective.
The synthetic stones, like diamonds also scratch grooves and remove metal to sharpen knives. I believe the synthetic stones are more efficient, predictable and consistent. By varying the density and size of the abrasive material imbedded throughout the solid matrix, during the manufacturing process, the Synthetic stones can be made to have a greater variety of predictable effects. As the synthetic stone with the embedded abrasive wears the stones wear away, what we call dishing. The synthetics have the advantage of being renewable by flattening them, called lapping, to bring fresh abrasive material to a level surface for continued use.
The natural stones are truly natural and are quarried from the earth like granite and marble. Different hardness, coarseness and abrasive natural stones come from different areas. These are then cut into useable shapes and flattened and polished for use. Natural stones are similar to some synthetic stones in that they form an abrasive slurry with water on the surface and this slurry is what actually removes the metal when sharpening. Some natural stones like Arkansas stones are used with oil.
Being natural I believe the grit rating is more varied and less predictable then with the man-made stones and can vary also in the same types of stones. I think there’s a mystique to sharpening with natural stone. A “Zen” kind of thing.
Last the ceramics stones are a whole different animal. They can be made of same minerals used as the abrasives in the synthetic stones but they’re melted, sintered, together and shaped into usable sharpening stones and rods. They are usually only finer grit stones and can be used dry. They also tend to be brittle and can break if they are dropped. The ceramics work because they are very hard on the order of diamonds. Rating they’re grit level can be difficult.
This is my opinion: The ability to manufacture synthetics stones with a variety of types, sizes and densities of abrasive I believe makes them more controllable and predictable for sharpening and therefore possible will cause less chipping. They are used with water, serving as a lubricant and cooling the metal surface. This may also help prevent chipping. Diamonds, called the hardest mineral, known to man, possibly with their narrow sharp points, cut deep grooves and I believe can catch on carbides in the steel matrix and being so hard the diamond doesn’t break, they break the steel matrix possibly causing more chipping. The abrasives in the manufactured synthetics stones can break down or wear off before busting the very hard carbides loose from the matrix therefore may cause less chipping.
I do think the acuteness of the bevel contributes to the brittleness and chipping of hard steels. I don’t believe these hard steels need to be sharpened to a fine polished edge to feel sharp, to cut and slice well and to be a durable edge. I have observed this with new, out-of-the-box knife edges of some of the super hard steel knives I’ve purchased. Fine grits are associated with finishing an edge, that is when the edge is its narrowest. This is when, IMO the hard steels are the most fracturable or chippy. Diamond stones as I related above are very hard and I believe with these very fine grits and narrow thin edges may perhaps cause more chipping than the less hard abrasives in the Synthetic Stones.