Uke does not have that choice.
I think they do... especially when someone has an injury or is not up to the skill level where they could safely take ukemi for the intensity of a particular throw. Of course, there are some to do it to test, but that can CAUSE injury to one or both parties. Unless... we're advocating not giving uke a choice at all and just forcing a technique regardless of uke's skill or ability physical fitness?
That's where my curiosity lies--when does it stop becoming cooperative practice and starts becoming an issue of whether or not you could down a person?