@Carsten: You are missing the point.
The main concept still present in your descriptions is that you still distinguish between tori and uke, therefore there is an implied difference in their behavior and/or the roles they follow in training.
When both keep Inside the kata, you can overcome a uke who tries to regain initiative within the kata, resist within the kata, keep low within the kata, etc. Their counter-actions are still honest and somewhat intuitive.
This is USEFUL training, because uke has an honest mind, generating honest reactions.
The above video is a siccinct explanation of what I mean. Anyone can cancel the tai no henko exercise, if they're not really in the mood to do tai no henko.
Same applies to most techniques as well. They're situationally applicable, which is why in jiyu-waza you can't just do whatever you want, but a limited range of technique which is suitable for current positioning and intent of uke. Maybe through a lot of dancing you can eventually Rubik's Cube the situation into a position and technique you want, but at that point this encounter loses any remaining martial applicability.
On these forums, George S. Ledyard (sp?) said before, that he can do a yokomen attack on which nobody can do irimi nage, if he knows what's coming and is fully intent on stopping it.
If you're in Judo randori, and the Judoka knows with 100% certainty the one and only technique you will keep trying on them, good luck ever throwing them. If you're in a boxing match and your opponent knows you only throw the right cross, you will never succeed. Both will use your railroaded movements to reverse what you're doing, use it against you.
It's an easily provable, common concept, and if you don't recognize its truth, then you are locked in the "dojo matrix". You are lucky to have such consistently honest ukes, even with resistance they give. They understand the situational nature of nage<->uke encounter, and play hard while still inside its bounds. This is good training.
However, eventually you will be exposed to someone who plays completely outside the game, and your experience will be jarring. You, or anyone, will not be able to throw such person without atemi or changing technique, as Katherine said in the very beginning.
Simply because their behavior changes the context into reality. In reality, you have to do what works in the NOW. Martial encounter means fluidly using opponent's weaknesses against them, and any schoolyard scuffle will have taught you that trying to do the same thing over and over will get you beat.
We do situational training just for that purpose, eventually do unite our situational responses into a responsive, fluid system of movement, which would be more suitable for dealing with reality situations than the hundreds of individual katas its built upon.
Making individual katas into reality encounters defeats their teaching purpose, and renders the training into waste of time.
So, let's please stop with this game of juggling definitions. Water is simply wet.