Yeah, 100 micro inches is .0001I agree, point it you can't really tell anything by looks. A lot of people think they have a great hone job by the looks and we are dealing with microns.
You'd be surprised what you can get away with, and I can achieve the same thing with my abrasive stones.... Recently did one with .9 .9 .2mm ring pack... Rvk was 100It takes good equipment but with the new coatings and ultra thin rings it gets very specific on the finish. I recently went from a diamond rough/ diamond finish to a diamond/cbn combo. The naked eye can't tell the difference bet the finish is much better when I measured it. Seems no to have as much rpk.