Right, that was Stan's point when he initially wrote that article. Pre-war, students spent about 5-6 years with Osensei. Postwar, he was in and out of hombu. So Stan's arguing that, because that's not enough time to correctly teach all the intricate details of his Aikido, the lesser-known prewar and postwar Hombu students developed in different directions.
Let's look at the Hombu people. How much time did Osensei spend at Hombu? I'm thinking he spent a couple of weeks a year there? So, probably a bit longer than AikIP students spend with Dan each year, right? People are training with Dan, going home with stuff to work on, working on it diligently, and everybody is saying they are making progress, it is opening doors, blowing minds, etc.
Now...given that the Hombu had uchi-deshi who were there to train 60 hours a week, as well as a lot of really dedicated soto deshi, it seems to me that if Ueshiba had a system anything like Dan's, the fact that he was not there very often would not detract from the quality of the Aikido there.
Osensei would roll into town, come onto the mat, and talk about the kojiki. He'd define what he meant in the context of solo training. he'd explain it as a physical process, and display power. Then everyone would do their solo training in their spare time, then next time Osensei came to town he would test everyone.
But he didn't. He didn't transmit this, it is not a part of his teachings.
I think that you're confusing the teaching method wtih the material being taught. Five different people can teach the English language in five different ways - are they teaching different material?
He outlined the method quite clearly to the post-war students - they just didn't get it, and admitted that themselves. When you look back at the material in context things become quite a bit clearer.
In any case, it's not just the amount of time that he was there - but that's another (and equally complex) discussion.