Re: What can you say about this?
Once a year I give a three-hour lecture on mathematical genetics. Every year I look at my note and slides from the previous year, and without fail I think I taught it wrong last year and there's some way to improve the presentation. When I haven't had time to revise the presentation and have just tried to give last year's, invariably it hasn't gone very well.
I don't think the facts of the matter have changed at all, but somehow the apparently right way to teach them in 1999 (when I first did it) now doesn't seem right.
I wouldn't be at all surprised if aikido were like this too, so if one was going to write a book one would have to accept a certain amount of ongoing frustration with it.