I've never heard anyone who claims to do an "internal art" say that collusion and a certain type of postural habit is REQUIRED for aikido (or Ikeda's aikido) to operate. It seems to be an even stronger statement than Michael Varin saying that the collusion was making it a bit easier for Ikeda. At any rate, Ledyard Sensei's more substantial experience with Ikeda Sensei seems to speak to a reduced dependence on collusion, not augmented, relative to what one might expect from looking.
Anyway, you called my partner non-collusive, in that he wasn't standing right, connecting his arm to center right, etc:
Ikeda gave a seminar at Northcoast Aikido once. At one point he formed a line and threw everyone using this instant ‘kuzushi katatedori'. Everyone walked up, grabbed his wrist and dropped to the ground like they're supposed to. When it was my turn I decided I wouldn't throw myself like everyone else, but not be stubborn about it to see what Ikeda would do. As I went in slowly to grab his wrist he understood my degree of collusion/non-collusion and had no choice but to abandon the technique. About six inches before I had his wrist he slapped my hand, and while I immediately pondered the awkwardness of the technique I admit I was slightly off-balance staring at our hands in disbelief. Right then he went in and pulled me down with my wrist, on a purely technical level I could have easily recovered and successfully resisted the throw but that would have been dishonest. My intent was thrown off-balance, that's all that mattered. Even if he didn't physically throw me down after, I would have bowed to him and walked off.
So, why was it so easy for me to take his balance, even in the high resistance portion of the video? If I am not depending on certain kinds of attacks, yet I am successfully doing 1/100th of what Ikeda is doing.. then I remain unconvinced about the "value" of collusion in acheiving kuzushi on contact.
Look at Ikeda, he never loses his balance. There is nothing to be gained from throwing someone else off-balance if you yourself go off-balance in the process. I'm going to be blunt here because I don't think you realize just how off-balance you are in that video. You could have easily been knocked over countless times from many directions. An unstable subjective ground is a grave fundamental flaw that affects one both physically and psychologically. No one with at least three months of Aikido training should be losing their balance like that especially in a simple katatedori technique. The staff would literally throw you on the ground if you attempted a multi-level resonator with such shaky ground. Once you fix your ground then you won't have to compensate for improper grounding anymore. Nage-centric grounding must occur first
in order to become nage, anything different including uke-centric grounding by default makes one an uke.