The Shoulder Relief Cinch actually changes the position and angle of the billets to prevent the saddle tree from interfering with the shoulder. The center of the cinch is set forward to sit in the horse’s natural girth groove, while the sides of the cinch are cut back to meet the latigos 2 inches behind where the horse’s natural girth groove lies. This brings the latigos from angling forward, to becoming perpendicular to the ground, which reduces the saddle’s tendency to be pulled forward into the shoulders. With horses that have shoulder interference without angled latigos, it simply moves the latigos back to keep the saddle away from the shoulders' range of motion.
The secondary benefit to this shape, is the cutback at the elbows. This gives more room for elbow movement as well, and prevents galls in the elbow area.