I believe the theory is the shorter dog bones raise the seat height and allow the rider's weight to shift forward (even though you should lower your forks in your triple clamps to complement the shorter dog bones!). The shortened length reduces the linkage ratio between the axle and the shock, meaning that as you would bounce over rocks and cause your rear wheel to rise and fall, the shock would be moving less as opposed to longer dog bones. This would reduce the bucking effect experienced over rough terrain.
