At first reading both statements seem mutually exclusive. However, there is a way for both views to be consistent if one considers that maybe Sagawa stated that he purposely held back knowledge because he didn't want to admit that he lacked the ability to clearly describe what he was doing.
Well if that was true, someone like Kimura (who Sagawa said was the only person he really taught) would not have the skills. There a testimonies of many people that can give account to that. Sure some methodologies are better articulated than others, but to say that Sagawa didn't purposely hide stuff from students is ridiculous. Sagawa must have had a clear methodology with intelligible language...if he didn't, would it have been possible for him to get to the level of aiki that he got to? Is it all "hard work" and no understanding of what he is training?