The reason offenses seem more efficient when using the no huddle at the end of halfs, is not because they are in the no huddle, its because they're usually not facing base defenses. Those chunks of yardage are a result of deep zones more than "hurrying up". The idea of using the no huddle in these situations is rooted in clock management, not because its a magical scheme that makes yards come easy. If simply going no huddle in any context resulted in confused & tired defenses, nobody would ever use a huddle to begin with.