If the parent had kept reading, they might have discovered the retroactive explanation of that sentence:

"This is the form’s real operation. Deadpan does not convince you it is neutral. It performs neutrality in a way that lets you enjoy both the performance and your awareness of it. You are in on the joke. The image says it didn’t choose, and you know it chose, and both of you agree to pretend otherwise because the pretence produces something valuable: attention."