He just did, most counterfeited stone is Nakayama, because they sell for the most money.
Almost any stone you see sold in Japan online is claimed Nakayama, no stamps no nothing.
Truth about Ozuko and Shobudani is they are more available, not hyped as Nakayama, so the prices are much lower.
They are cheaper because the hype machine has not cough up with them. Ozuko especially produces harder stones that are very good for razor. Nakayama produces softer stones that are more for tools and knives, rarely you will find real hard Nakayama, I mean as hard as some Ozuko.
Currently the trend is Nakayama prices are going up a lot, kiita especially, who knows why but it is a fact. From what I hear a good size and quality nakayama kiita is not less than $5k now in Japan, good that the Japanese do not value Asagi so much. Other mines that have big price increase are Okudo and Ohira, all this comes from huge demand by carpenters, and other craftsmen that sharpen tools on Jnats.