I agree.
One of the tasks of an instructor is to 'unload' the mental capacity of the student enough allow better (best
) performance.
Usually this is done by the instructor doing some amount of the total workload that the situation demands. As the student gains skill then more & more of the whole workload is given back for the student to do.
Other ways include limiting the environment so that the overall workload demand is lessened, using ground training to develop workload capacity prior to it being needed in the air, etc.