This kind of discussion always inevitably makes me think of my training as an Alexander Technique teacher. I haven't had training that intense in aikido at least until now.
There's a saying about the teacher training process (the training course is typically about three years) that I've heard in various forms from people on different training courses, so it seems to be somewhat universal, that goes something like this:
First year student: I don't know, but I feel great and I love this training
Second year student: I don't know, and it's driving me nuts, and the teachers aren't helping
Third year student: I don't know, and that's OK
...and then you graduate...
Anyway, the letting go of the need to know that happens towards the end of the training, wouldn't be meaningful without the need to know during the training. Otherwise people would stay on the level of first year students forever.
I don't know how this would compare to a process in aikido though.
Letting go in general... it's an important tool in what I do when I teach, but it's not the only tool. Alexander pupils often fall into the trap of just letting go, but if you let go of everything, you end up a directionless noodle on the floor, and you still haven't really addressed your habits in a meaningful way. That said, once you decide on a direction, it's also necessary to see how you are stopping yourself from going in that direction, and letting go of that. Otherwise there's going to be conflict. There's going to be conflict anyway because it's not possible to see for ourselves all the ways that we stand in our own way, and so there's always going to be something stopping us from going where we want to go.
When a real change takes place it all happens in the same instant, the wish to enter something new, and the letting go of the old, the feeling that this new thing is artificial and "wrong" and the realization that it's giving us more freedom and space, but that we might possibly die and it would really be safer to go back to the old known comfortable...
I don't know if I'm even on topic anymore, just thinking out loud and in a bit of a hurry.