Having some direct experience with Ikeda sensei, my thoughts:
1. What Ikeda sensei shows in his seminars is based upon the presumption that those attending have a basic understanding of proper structure and body alignment. I believe he also expects most in attendance to have a basic comprehension of technique.
2. I believe much of the instruction Ikeda sensei is based upon layering on top of proper structure and alignment internal movement that strengthens the entire shape. I believe this is the advanced level of training where Sensei is showing "make connection."
I think Jon touches on a key point here. I have been going to seminars with Ikeda Sensei for 20 years, and while that isn't nearly as much interaction with him as someone like George Ledyard has, it means that I have been watching him and working on what he teaches for a while. Back around 2000, two students of Ikeda Sensei - Ron Meyer and Mark Reeder - published a book titled Center: The Power of Aikido
that attempted to capture in dialogue format many of the concepts that Ikeda Sensei was teaching at that time in seminars. The concepts were things like centeredness, relaxation, alignment, connection, grounding, uprooting, spiraling, timing and position. I bought a copy of the book when it first came out, reread it a few times over the next five or six years, and consciously tried to work on incorporating these principles into my aikido (others are in a better position to judge how successful I was). But what I have noticed in the past few years is that the time I put into understanding those concepts from seminars Ikeda Sensei was teaching 6-12 years ago has helped me understand what he is teaching now in seminars.
So not only would I agree with Jon that how Ikeda Sensei now approaches seminars involves "a presumption that those attending have a basic understanding of proper structure and body alignment", but I would suggest that much of what he presumes is outlined in Ron and Mark's book.