Stanley is shown stories that appear to say one thing but a…
Stanley is shown stories that appear to say one thing but are interpreted as saying something quite different. The first two stories are about misunderstood monsters who use deception to gain acceptance by society. Yet Stanley is told that they mean that he can just "be himself".
This can be understood as a kind of hypnosis or inception. If he is distracted enough to forget his apprehension of the idea to use deception to become accepted by the other children, he may still accept the idea somewhat unconsciously.
However, he does not appear to use deception on the other children, so how does the deception of the story relate to his real life? Stanley does use deception, but not against the children. He uses deception against himself: he tells himself that his true identity is a piano player, not a normal kid who desires friendship.
The only time he plays the piano in the story is to show that he is superior to the guide. There is no evidence that he ever plays the piano for fun. Instead, the piano is a lie that he tells himself to produce his feeling of self-esteem. It is something that the other children don't to, something that makes him superior to them. If they don't accept them, so what? They don't play the piano.