The idea is that your hand is more open and relaxed and rest against the swell, instead of clinching to "choke" the rifle. More and more competitive shooters are using the "free recoil" technique, so the pressure against the gunstock at ANY POINT is minimized. The large palm swells, thumbholes, etc etc are designed to help put the shooter in a relaxed, nearly anatomically neutral position. The nearly vertical, enlarged pistol grip with the large palm swell puts the shooters trigger hand in a nearly neutral, relaxed position, and allows the trigger finger to be limited to the horizontal plane, letting the trigger pull be drawn perfectly straight rearward.