tompoland What I mean is that )perhaps) if you shave say 1 micron off the circumfrance of a rock then not much changes but if you take the same amount of a spec of ground coffee, it will be more effected.
To put some context on this, espresso grind typically falls roughly between 200 & 450 microns avg. particle size (the smallest particles are single digit microns, the largest particles over 500um, up to maybe 1500um).
1 micron makes no difference to anything, anywhere.
Sweet spots depend on brew ratio. As grind requirements get coarser, the deviations in specific particle size get larger (the difference between 1 & 200 is smaller than 1 & 800), as do the deviations in terms of distribution of ground mass vs the average grind size (sdev factors also get larger).
E.g. if your average grind size is 400um and the sdev is factor of 1.4 of the avg. you have -114um/+160um for one standard deviation either side of the average (68% of the ground mass). At 700um and still at a 1.4 sdev factor you have -143um/+200um for the same proportion.
In absolute terms then, grinding gets less precise the coarser you go, but in practice this doesn’t seem to be a problem.