This sounds like what I think of as "tracking." Once they're both in motion, uke shouldn't be able to track nage, ideally, and if they can, but are not, it's an example of collusion. Does that sound right?
I'm not sure if I can understand what you are trying to get across.
The type of following I am describing, looks and feels like collusion until nage makes the slightest mistake, which then becomes apparent by a 'clash' with the uke, providing uke is following in the way I describe in the OP. This is completely different from colluding with nage and just going with the technique and being thrown whether the technique is performed correctly or not.
This has to be seen as a sliding scale, if I followed a beginner like this, they would never complete the technique successfully. If I work with a beginner, I will almost do the technique for them so they learn the outer form. The higher the grade the more intensity of the following.
I make it my focus to track everything that nage does, but my primary focus is on myself staying centred, fluid, flexible, sensitive and solid. I'm here to help myself and my partner improve.
I know this type of practice is not common in all styles of aikido, as I have come across those from other styles, who do not practice in this way. What does become apparent is that, they are not used to dealing with this fluid/solid paradigm.