I think people inadvertently put pressure on kids without realising they doing it. Big girls don't need comforters; it's time you grew out of that; big boys can use the toilet; the proud mum boasting my baby was dry right though the night at 9 months! The praise that they give for getting it right. These are all things I have heard parents say to their children or about them. And they learn that grownups do things like that in private, with the bathroom door shut. I remember my nephew bursting into tears because he didn't make it to the loo in time at home. His parents explained that he had wanted to impress me by not needing help to go. There is no way that anyone had put any pressure on him in this matter - except maybe by praise and encouragement for getting it right. On the other hand, there are those who are cruel too.
I think that the incident is indicative of the way Gilbert reacts in the future to authority. He submits, essentially. He may try to control his emotions, but he is still not in control. He does what his Momma wants, even when he knows it is wrong, such as with the food. Even when he tells her he hates her, it is at her instigation. I think there is a similarity also with Mrs Betty Carver, with her making the decisions - certainly about when to meet. It would have to be that way, with her being married.
It also establishes a pattern with his feelings about the fake smiles. He is most worried about Amy when she smiles. The fake smiles crop up frequently but my favourite is "The citizens of Endora keep their rage and disgust quiet; their smiles and friendly nods are like fabric conditioners for the face."
"Luck... inspiration... both only really happen to you when you empty your heart of ambition, purpose, and plan; when you give yourself, completely, to the golden, fate-filled moment."