I said self-trust is crucial to good ukemi. If you can't trust your own actions, you're going to hesitate from time to time and that's often the kind of thing that gets people hurt. As uke, I never fully trust nage. Stuff happens after all, and if I assume it won't for the sake of trust, I can get hurt. You might say the only thing I trust is the uncertainty of the world around me. In that context, trust in myself seems the more certain option since I at least can control my responses to the situations I have relatively little control over.
I agree with you, but I have two points. 1) A good nage can sense when he/she should pull back on a technique or a throw in order to save the uke esp. when they can tell that the uke is not ready or maybe a little afraid. 2) Uke should know when nage is not paying attention and bail out, if necessary, in order to save themselves from injury. I know someone who decided to take that approach after he got injured by a thoughtless nage.