Is it unconventional? Yes. Very much so. But Bill Walsh was unconventional when he introduced the West Coast offense. And then he won three Super Bowls.
Let me explain:
First and foremost, it gives three players a much-needed rest in the closing minutes of a tight ballgame. By using only eight guys on the return — as opposed to the 11 traditionally used on, you know, every play in a football game — it allows three additional men to catch a breather and a swig of water on the sideline. That can be the difference in an extra burst of speed or effort, or cramp prevention, later in the game.