You turned my post by 180 degrees
and thus you spoiled it
I agree, that there is a good chance, that - especially in demonstrations - a supportive uke or even a pre-arranged choreography make it a farce. And from outside - at least for me as an amateur aikidoka - it is hard to detect.
I have not seen or even those wonderful great techniques, but in videos and one of them was definitely a fake - the one when uke had to lay down and went even unconcious, just because the "big sensei" looked at him.
However I have experienced simplier experiments, e.g. I tried to hit nage with yokomen uchi and nage did not move but put an atemi just in front of my nose without touching me - and I promise, at least the third time, I really tried to hit him, but I was not able to touch him. I have seen similar things on a seminar, where the sensei had to use an uke even of another organisation.
Nevertheless there are good reasons to use only experienced uke for high quality techniques.
1) You have to be very good to predetermine the reaction of a person, you have never seen before. So you better take an aikidoka, whom you have at least watched on a seminar and/or tested with some simplier techniques.
2) Even if the technique works, it might not look good, if uke does not know to roll, when he looses balance.
3) If uke does not react well, he might get hurt by an atemi, he did not avoid (only second level quality, as obviously you touched), or by a fall, he was not used to and could not manage.
But again, I agree, we should not care too much about it. When we feel, we are good enough to do those techniques, it is early enough to check details. I am just still a day dreamer.
For the next time, you choose me as uke, I can promise you: I will not be so stupid and resist to hitting a sensei, while he is still talking. I will just do, what I am told. At least I try my best not t make you look good, but to make me the king of the day
Have much fun - until then