However, when he does so I do not believe he is teaching what you refer to as "aiki" (the definition of aiki being internal strength). It is certainly possible for one to read into these exercises and see something else though.
Just want to clarify here... Have you checked with Saotome Sensei on this? Because I'm pretty confident that he sees aiki as the core of his art. (Which is, after all, called AIKIdo.)
Speaking for myself, I'm also not sure that I would agree that "aiki" and "internal strength" are the same thing. Certainly internal strength is an *aspect* of aiki, but (re)discovering internal strength wasn't Ueshiba Sensei's great insight.