Don't worry, it's not a silly question at all.
I agree with the two other answers. In fact, this is quite a common obsession among young children in some countries in the west. Some small children, especially boys, do sometimes insist that there should be a small space between everything on their plate. They get upset if the meat is in contact with the vegetables, for example.
I realise this must seem weird to someone from Asia, where dishes combining many ingredients is the norm. I guess it would be difficult for a Korean child to insist that nothing on his plate should be touching anything else. It's also sad that a small proportion of people, particularly those with tendencies towards Aspergers, autism or OCD, carry this on into adulthood.
As for the scene in your movie, the purpose of this comment is to show how thoughtful and indulgent the mother is being towards the child following his traumatic experience.