If they had been riding in a car, she would have waited for him to go around and open the door for her, but riding in a truck is different
"If they had been riding in a car, she would have waited for him to go around and open the door for her," highlights a kind of traditional courtesy, emphasizing male consideration in everyday situations. It shows the difference in social expectations depending on the mode of transportation and surroundings.
In contrast, the quote suggests that riding in a truck alters these conventions, implying a more casual or less formal atmosphere. Beverly Cleary uses this detail to illustrate how settings and circumstances influence behavior and manners among characters.