Oh I was watching once again your videos. A related one was this:
Under this respect, my half-humorous and half-serious answer becomes more serious - for: tell me, in this latest video, what's the difference between that "iriminage" and hitting uke in the face with a punch: wouldn't he likely fall in both cases?
Some techniques seem stuff to put in store for when you become a demigod at Aikido - when the techniques flow so spontaneously from your hands that whatever incoming dynamic immediately elicits its appropriate response.
That is: you need to be able to extract the Sword in the Stone first... then yes, you can secure any fight. Undoubtedly.
However there are so few at that stage (certainly not me!) and it would need so much training with ukes of every flavour, that my suggestion to ground him seems less unwarranted, and less humourous - after all, in that video we see an 8th dan throwing a _dissimulated_ punch at one's face!
Let's call a rose with another name!
Actually, with ude kime nage one would think that the more the arm is rigid, the better. Maybe this: try irimi badly into his armpit and give a strong hip thrust, and get ready to drop on him when you see it did not work?
I really don't know. Some techiniques are a big mistery to me and when you say hey they don't work if uke is very aggressive and/or strong and/or rigid I'm all with you.
IMHU is comical. They probably meant as a demonstration of how we can make people laugh :-D