Please don't hold me to this. But, I believe I remember Lynn Abrams saying he lapped the Naniwa Superstones when received. But, again if I remember correctly, the reason was that he thought the consistency of the "stone" at the top of the hone was not consistent with the rest of the hone. He had to lap thru the thin layer to get to the regular consistency.

But, heck! It might have been anyone who said that...

Whoever said it, it makes sense to anyone who has poured concrete. Gravity pulls particles downward before the concrete sets. But, I wander...

If true, I doubt it would be very critical.