heck, people who tried to cancel a technique is everywhere, I find it especially in newbies. but that's because they're not exactly resisting in the capacity of an uke
a good uke is one that attacks realistically, the way an assailant would, but can protect themself (ukemi) when the technique is executed on them.
in order to achieve a realistic attack, ideally an uke must not guess what technique the nage will execute, or in which direction he/she will be thrown. The uke must also attack with a focus; cleave the skull, cut the neck, hit the jaw, stab the abdomen, run them through.... all of them an acceptable visualization for an attack.
instances where the uke set his mind to cancel nage's techniques should be limited to special occasions. or in advanced class.
white belts with this tendency should be warned off this attitude when training with other white belts. I personally encourage them to experiment AFTER the training. With me.
so basically I vote that uke can't be wrong. But they can be exasperatingly un-cooperative and unbeneficial for the training.
as for ego... well, that didn't have a place in the dojo.