The first four balls are close combat: the serve, the return, the 3rd ball, and 4th ball.
Close combat accentuates both the upside and downside of a situation. For example, a good volley can finish a point while a bad volley can lose it. The point will end either way.
That's why they call it a one-two punch. A serve and 3rd ball or return and 4th ball will dictate how the point ends. Once a 5th ball is established, the point becomes far more structured like playing a point off a drop feed where you'd have to construct the point. Know your strengths and weaknesses to determine whether you'll do more damage in close combat or a structured scenario.