This is a great stretch to improve your ability to hinge your hips and rotate your torso.
Being able to properly hinge your hips will help your set up position as you address the ball. Typically, I find that clients who have difficulty hinging their hips will tend to round from their upper back as they lower themselves to the ball.
This creates a number of issues. One being a limited shoulder turn/shortened backswing, where the club gets too inside and causes an over-the-top swing. It can also result in a loss of posture as you stand up in your backswing to create a bigger turn.
This exercise kills two birds with one stone – your ability to get into an athletic posture (hip hinge) and make an athletic move (torso rotation).