Lost count of how many Carl!
At first I put it down to the extreme hardness of hones like LIs, Arkies, CFs and the like - its discouraging enough having to remove a mm or two, but I have found it with even greater regularity with coticules, which are much easier to lap.
Strangely enough, I have had a fair number of old natural BBW/Coti combination hones where the BBW side has been dished to such an extent that it has gone right into the yellow layer - really extreme dishing!
I have read posts by contemporary users of jnats, though, who advise that they don't bother lapping. Seems like the one stone with a variety of rubbers was used so that the slight dishing was not a problem for them.
Regards,
Neil