Example: at two recent seminars, Ikeda was teaching and people on the floor were using my descriptions to help each other actually do...what he was doing. All they got was "Move inside." That doesn't nearly cut it. As one American Shihan said at another get together when the Japanese teacher sat down. "I will now explain what he did...and how to do it!"
First, I love Ikeda Sensei. He's a great guy. He's an extremely talented martial artist to boot.
BUT, I don't know how many seminars and classes I've been to of his where he would say, "working! not working. working! not working... OK you try..." and that would be the extent of his explanation. Totally useless. If you already knew what he was doing, it was fairly obvious what the difference was, but if you didn't there was no exposition to get there.
I think it actually makes sense that the Japanese would be bad at explaining things like this. You have a language that prides itself on being vague, where the more specific you are about things, the more you have the potential for being rude.
I think that some of that culture may be changing however. I actually gave a presentation in California last week to a room of senior IT folks from various Japanese corporations and they asked almost fifteen minutes of detailed questions after my thirty minute presentation. I was genuinely surprised.