I guess they are acting right away instead of waiting for the paperwork to get sorted out.
Not really seeing this as a haha funny moment as much as it is two people who realize their marriage isn’t going to work out having a calm and rational discussion followed by being supportive of each other. Well, it isn’t long enough to show the passenger being supportive, but kind of assume they must be based on context.
The rubber duck method is just another flavor of thinking out loud.