This is a great exercise for two reasons:
- Students feel the sensation of air movement which is a much better thing to focus on than any body movements or where the air is headed
- This lets the student experience firsthand the difference in efficiency when they inhale with a good oral shape
Combine this with the "EE to Oh" exercise out of the brass gym and you can fix a whole lot of breathing issues without ever addressing them. And in teaching, using fewer words means less chance for confusion and getting to the actual doing of the activity being addressed faster.