OP- you're not asking why the rider is using a crest release, but why such an exaggerated crest release, correct?
1) Georgina Bloomberg had some excellent quote about riding a hunter... something about how the ideal hunter should go around like a blind dumb monkey could ride a perfect course. Some riders like to go around the ring with a huge loop in the rein to "show off" how easy and simple their horse is to ride.
2) everything Maura said in her first post about the horse jumping in a relaxed frame.
3) It's easy for some pros to get sloppy. In any discipline really.