George had a very interesting post. It really adds to the learning curve for being uke too.
On a simpler note we have been told recently by our Shihan to include training where uke pushes and pulls (applys to grabs and strikes).
I think this is a step used to develop the feel for your response. I also think its part of static training and is intermediate to the leading and Kinonagare training George speaks of.
1. Static - neutral, ie: just hold in place firmly
2. Static - push or pull
3. Kinonagare - blend, lead
It was suggested to us stage 1 is kept to until a student does their 1st test . Stage 2 is introduced after that. Not to say that basic static training won't be used throughout training as a learning tool by all ranks.
The 1st stage may be the foundation you mentioned. It allows the student to learn their tai sabaki, etc. Once that is in place then the dynamic aspects start to be worked on. I know for myself anytime some new movement is shown to me I like to go back to the basic static mode and go through the form until I think I get it. Then I can begin to work out the blending and feeling part.