The unequivocal testimony of senior practitioners of KSR is that:
a) Inaba was given access to a very limited portion of the curriculum, for a very limited period of time, and that the combination of circumstances was insufficient to give him "the goods" (which goods are swordsmanship as practiced in KSR, as distinct from a marked improvement in his swordsmanship above that of run-of-the-mill aikiken).
This is a case where different stories are coming from different people - "senior practitioners of KSR" vs Inaba sensei (and others). I have had unequivocal testimony from Inaba sensei! In the absence of independent third parties (and it's over 40 years ago), it's a "he said, she said" scenario - with obvious motivations/bias on both sides - so people have to make up their own minds as to who to believe.
Apparently there may be some relevant articles in "Akamon Aikido" a bulletin published by Tokyo Daigaku Aikidobu and Akamon Aikido Club back in the 70's - no idea if any archives exist.
I am not comfortable saying much more on the topic in a public forum - but did wish to at least present the fact that there is another side to the story - more than just the one sided version previously put out on the web. If you wish to discount it, that's your prerogative.