The two are "only" exercises and both have their point. In the second you breath in the position you will breath in whole stroke. In the first you roll to air.
In whole stroke you also roll to air, but you start in the skating position on the other side. With the stroke you roll the body from the skating position on the one side to the skating position on the other side where you breathe. In whole stroke you can't roll so far as in the first exercise, this would lead to instability, but you can imprint the rolling motion with the first exercise, the correct position with the second.
Best regards Inge