Yeah, they like to say that in the book, but the reality is that hard stones that stand up well to hard irons all will release particles when the metal is soft. It only takes spring steel to do it, and anything softer will do it, too. I don't think that it's silica impurities pulling particles loose, I think it's the fact that the soft metal can be cut deep enough to pull the particles.
I've got some hard japanese stones and some oilstones, and the same thing is the case for both. A medium hard pocket knife will partially refresh the oilstone, which is a bit of a disappointment, and any japanese chisel or plane iron will do the same to the hardest japanese barber hone that I have (though with hard steel only, as it would see on most razors, it will not let go of any particles).