This is exactly correct. Japanese culturally don't like to step out of line.
Please. That sounds so ethnocentrically ignorant. I used to live in Japan, kids these days are all over anything new and unusual. Especially tech shit. Especially American shit.
Step out of line? Have you seen what Japanese get into for entertainment over there?
And if you say that they wouldn't be interested in Bitcoin because it undermines their government, Bitcoins have not gotten big enough to have been declared an anti-government activity(yet). It would not at all be considered "stepping out of line". And there is no way they are more authoritarian than the Chinese, and the Chinese are leading the client download chart right now.