I have no idea about those cartridges but being somewhat expert on Japanese woodworking tools, the Japanese tend to hoard the best stuff for themselves. They export the second grade stuff. To get a decent hand made dozuki you have to know someone in Japan to get it for you. It would not surprise me at all if Japanese home market cartridges are superior in some way to the ones they send us.
Interesting. I bought the Otono-Edison without knowing what to expect, it was a blind deal. When I bought it, I already owned Miyajima Kansui for a few years. Now my interest in Miyajima or Edison cartridges raised to the stratosphere level. It's so pleasant for my ears, now I understand rave reviews about Shilabe when it was introduced many years ago.