i think that t works both ways.
uke has to be relaxed and respond to the technique. this way injuries are less likely, and it helps tori.
though if im uke, and the technique being done has no effect (e.g not being done correctly, or with any amount of force at all) i wont go. how else would tori know that they are not doing it correctly otherwise.
aikido is all about blending and working together in order to enabe the technique to be carried out.
in the past, ive found that if i have an unwilling or unresponsive uke, i get shouted at for not doing the technique correctly (either because it wont work at all or because i have to adapt it in order to make it work). the same went for thursday night when i was uke, and i wasnt falling right, it messed up my partners whole form, and i felt very bad for that.