I t is always easy to disavow points one does not like by merely attacking their authenticity without actual attribution of a source of error in transmission. So why should you do that -- who says so?
More to the point -- why trust the Japanese either? Most of them were transcriptions of what he said, rather than his own writing. The entirety of the Takemusu Aiki lectures was transcribed stenographically as he gave it. Budo Renshu has the distinction of being one of his two major pieces of actual extended writing on the subject, so at least one source of error is removed. What basis do you have to question Bieri and Mabuchi's translation?
I don't think it is a matter of questioning the translations as much as the fact that any translation from Japanese into English is going to be essentially limited. You start with the fact that O-Sensei's usage was arcane even for the Japanese. Then you take that and try to translate it into a language that simply doesn't have the same concepts in its culture. Any translation is just an interpretation.
If you take a look at the Tao Teh Ching the Chinese is open to multiple levels of interpretation due to the nature of the language. If you don't read it in the original, you lose those multiple levels. However, the book is the single most translated text in Chinese (other than Mao's little red book which doesn't count as far as I am concerned). So if one, as a non reader of Classical Chinese, want to get some picture of what the original meant, you need to read a number of translations and compare them. Each one will convey some sense of what was meant.
O-Sensei's writings, such as they exist, have not been given anywhere near the same amount of scrutiny. There are not multiple translations for us to compare. So any translation is limited. Even a Japanese speaker not trained in the specifics of what O-Sensei was talking about would be interpreting when he described what he thought O-Sensei meant.
Therefore, all of this discussion of what O-Sensei meant or didn't mean is subjective. I might have a take on it based on listening to Saotome Sensei talk for hours about training with the Founder. That helps me create a context when I read the writings. But it's still not cut and dried at all. I believe certain things about what O-Sensei meant in his writings. It's my opinion. It may be an informed opinion, but it is essentially based on incomplete information. And there is no way around that.
Then, to complicate things further, it is a fact that when O-Sensei's lectures were translated into English, the translation was specifically tailored to make a certain presentation to a particular audience. What was translated was cherry picked and how the terms were translated was controlled to create a picture that fit what the folks running the show at the time wished to present. This was not translation done to exacting academic standards, it was translation to create an impression. This wasn't true of he Doka translations by Larry Bieri but it was true of some of the other material that shows up in books about Aikido in which O-Sensei is quoted.
I think at this point it is important to know as much about the Founder as possible but we will ultimately arrive at our own understanding of what he meant through practice. I hope we can avoid a Council of Nicocea at some point in the future at which some orthodox interpretation becomes written in stone. The discussion and the personal discovery are everything as far as I am concerned.