I do like your list for the breaking points as they pertain to razors, the labels could be changed for personal preference.
The average dimension is decreasing, but there is a nonlinear edge that remains just about constant. So really you are just smoothing out the irregularities after ~1k.
There's nothing to buy into, that's just the way it is. :D
The function of the tool cannot be left out of the question. A nakayama is the zen-stone for a razor, but it's a "waste of time" stone for a utility knife.
Both must be sharpened, but the intended use determines the label you give the stone that each is finished on.