Peter A Goldsbury
I would like to take the discussion one step further and separate the matter of what is being demonstrated from the description of what is being demonstrated. You can imagine Mr Ikeda simply demonstrating what he is doing with no commentary, but it would still not necessarily be a demonstration of IP. My point is that even if you take away the commentary, you are still left with the problem of the gap between what people think they are doing and what they are actually doing and this would apply to others besides Mr Ikeda. It might apply to Morihei Ueshiba, for example.
I think this applies particularly to one old teacher of yours: Kanetsuka Sensei. I believe he has a high level of this kind of skill himself, but - will all due respect to him - I think he struggles constantly to explain what he is doing: he uses a whole arsenal of metaphors, as well as many explanations in terms of physics (for which I feel I am a perpetual disappointment to him in my failure to clarify them), but the class is often more confused than edified.
I remarked to him a year or so ago that he never explains to us what precisely he is doing to his uke, and his only partially helpful reply was something along the lines of "tori and uke are one, so uke moves". He has also said things like "I swallow my partner into my hara, and then sick him out again" and "cut your partner down to his knees then back up again", but these are again hints, rather than concrete instructions. I am starting to understand a little of this kind of imagery, but all the same I often wish he would tell us what he feels in his uke's body when he moves (perhaps in the way that Ikeda Sensei says "find partner's tailbone").
Feeling his aikido in person tends to be a completely different experience from listening to him teach (and to some extent from watching him demonstrate): trying to work out from this limited exposure what he is doing - and also what he is not doing - is fascinating and frustrating in equal measures. As Phi says, the experience of holding a teacher's arm can give an altogether different impression than watching someone else do it.
What he has been saying in recent years, which I am taking more and more seriously, is that his aikido is based on just a few solo exercises: torifune, furitama, qigong-style arm-swinging, as well as the makko-ho stretches. He also used to practise a sequence of suburi (either with a bokken or shinai, or empty-handed) from seize, kiza, sonkyo and kibadachi stances. Nevertheless, he still teaches even these exercises mainly in the old style of demonstration and repetition, with little in the way of explanation of body structure and alignment. He often cites the model of "stealing" the art from a teacher: he admits that he is only just understanding in recent years some things he watched his own teacher do forty or fifty years ago, and perhaps he is expecting us to absorb these things almost passively and then process them unconsciously in the same way.
Alluding back to the subject of this thread, he has released teaching videos over the years which are very useful in learning the form of his aikido, but these are purely formal demonstrations of technique with no explanations at all.