Thread: Japanese Grit vs. American Grit

Ok, so a discussion in this thread has kind of brought home some different ides I've been thinking about for a while.

It appears that some of the Japanese synthetic stone makers have some stones that are not available in Japan that ARE available in the US, and vice versa.

For example--there is NO 15,000 Shapton Pro series (刃の黒幕 in Japanese) on the Japanese Shapton website. The closest thing is the 12,000....which, oddly enough, in the color coded series is the same color-cream. According to JimmyHAD, who has both, they are largely indistinguishable except that the 12,000 feels softer. Hmmmm...

Then we come to the Naniwas. The Super series in Japan does NOT have a 12,000--only a 10,000. (here's the same site in English, NOTICE STILL NO 12,000!). This time, however, the coloring is different...

So, here is my question.
If these stones are made in Japan, by Japanese companies, why oh WHY would they make a higher grit, and therefore more expensive and more effective for polishing, stone exclusively for a foreign market? Especially considering that they very likely are MADE AT THE SAME PLANT?

Here are the some possible explanations I have come up with.
1. They feel that since the American market is bigger, it might be more willing to pay a bit more for the slightly higher grit (unlikely--Japanese tool users are VERY willing to pay high prices for quality...).
2. The Shapton stones are, in fact, identical but there is a difference in grit rating in the US making a Japanese 10,000 equal to an American 12,000; 12,000 to 15,000 etc. (JImmyHAD, who is experienced in these things like I never will be, says they are different.) This would also be unlikely, since the other stones have the same numbers...
3. The Shapton stones are identical, and they're just saying it for some weird reason that we Westerners could never understand. Probably something to do with Ninjas.

I go with number 3. Though none of this explains the Naniwa stones....because they still have a 10,000 in the States, right?

Soooo...what have I missed?