That is the impression I have too from what I have read. The one that I got from Ardennes fits that description. As Randy and Russel frequently point out all natural stones have different honing characteristics. I have a natural coticule and it is a fast cutter on either side. My tiger stripe is not as fast but it is a good hone.
My kosher is a finishing stone for sure. It is not nearly as aggressive as my other two. All coticules and all cut a bit differently. I have heard that rabbis who do the circumcision seek out perfect unblemished stones and maybe that is how the kosher label came to be for those stones ?