Of course nobody likes a guy to score the points and then run around but it is not against boxing rules. Let's take any sport for example, say, soccer. One team scores 2 goals and after that decide to just pass the ball around and make time. Sure, the crowd will boo, they might even throw stuff at the field, but they would go home with their win.

If a guy scored points, connected his opponent, etc. and boxed around or prevented engaging for the last 20 seconds of the round, I would give him the round. Why not?