Here's my take. For cars with stock spring hangers the loads are being transmitted at that location. That is why Chrysler made torque boxes, to connect the thrust to the frame rails. By using the Hotchkis style, you are strengthening the unibody in the right areas and eliminating the need for torque boxes. For cars with inboard springs (in the framerails) putting the connectors in line with the rear frame rails does the same thing. I believe that on most cars the spring hangers line up with the front frame rais as well.