Our dojo has the unusual arrangement that the official Sensei sometimes "merely" participates with the class while another black belt teaches. The arrangement has never been explained but the gift of the situation is that on Saturday's you can often personally learn from the Sensei, one on one.
Today we practiced kokyu nage and Irimi nage and I was working with Sensei on a type of kokyu nage (breath throw). FYI, one thing about kokyu nage is that there appears to be an endless variety of them. Anyway, Sensei pointed out that for this technique I should not try to anticipate what the technique intends, rather act as if you didn't know what would was to come and you as uke then react spontaneously
All well and good. Except you are often advised, as uke, to react and move with nage's technique. And once, I was advised by one teacher that I, as "uke", should know what was to come and to act accordingly. There are sometimes instructions about not causing too much resistance yet also instructions that being a good uke means committing fully as an attacker. The positive spin is that this is another example of the wonderful complexity of Aikido. the negative spin is that you never know what to do.
I could not find a YouTube example of the exact technique we worked on, but this clip does exemplify how being an uke means many different things. Attacker, follower, knowing how to attack and respond. Some people might think the Uke is stupidly following a course no normal attacker would, but that would be to miss half of Aikido. The "uke" part.