The snap down back handspring is a very helpful progressive step toward the round off back handspring.   Advanced gymnasts may practice this combination to refine some back tumbling technical details such as turning over from hands to feet on a hollow single body unit and  rebounding with a tight arch first flying phase while the  shoulder area is open.  This gymnast is trying to turn over some more during the snap down.  He is squating a little too much  he needs to turn over and rebound more.    /Last turn/ This example has a little better turn over than the ones before.