Dreaming with the deck under the pillow does not change the relationship with the deck. I did not intend to suggest that sleeping with the deck and dreaming was a method, sorry for the misunderstanding.
Not to say that it can't BE a method. A dreams 'direction' can be created with anything. This gets a little off topic, but it ties into the subject and I see that there needed to be a little bit more explanation.
In the area of dreaming, and not tarot, this method of directing a dream is called ‘inoculating’. This is where a person gives their dream a direction to go in. This can be done by way of meditation before bed, or, in cases like sleeping with the deck under the pillow, by simply focusing on something and having that something with you when you sleep.
Dreams themselves, without being given direction, will use the events in waking life to create the dream movies. So anything you do through the day or week can, and likely will, be used by your dreams. So by putting a deck under your pillow and not purposly directing your dream, it is probable that you will dream about tarot.
I have not personally done so, at least not intentionally. I have fallen asleep while studing my cards and they 'slept' next to me. But if I dreamed about the cards, I do not remember.