Prince, I can only speak about my dd's early programme, and the imitation trials she did.
In her case, she was so demand avoidant, and scared of trying in case she got something wrong (even when she did actually know the right answer/could do the task), her self confidence was through the floor.
She was asked to do a lot of easy imitation stuff at the table (and easy matching/posting/sorting) to increase her confidence. To help her see that there was nothing to worry about. to try to build a trusting relationship - that her tutor would not ask her to do anything she was not capable of doing. to try to get her to enjoy the things she could do, before moving on to doing more difficult tasks.
It didn't always work, of course. She stayed worried (and still does, 6 years later), and was not always comforted. But it did help to build the trust, and she did relax enough to make other learning less painful for her.
She still needs errorless learning now. And she still remains very anxious, and unable to answer if she feels she may be wrong. But it is improving.
It has the dual purpose of increasing compliance - she got used to doing as the tutor asked, since the task was so easy for her. It then became easier to slip in a couple of new simple small tasks to get her trying new things.
The quick fire imitation tasks also help to break down inflexible thinking - a chain of trials, all easy, but quickly asked and delivered, with no routine about it, cna help to train quick thinking and sudden changes of direction - to begin to expect the unexpected, in a way, iyswim?
It is a long time since I was involved in these type of trials (I can't believe it's been 6 years since we started ABA
), so I hope I have remembered correctly, and explained it well enough 