What the Strong Mount does is not so obvious until you start using one. If you directly bolt the press to the edge of the bench, then there will be a huge tendency toward more bench deflection, simply becasue the press overhangs the edge on a very small "footprint". Any movement in the bench is the direct result of your muscle work. Therefore, any bench deflection represents wasted energy you had to use to operate the press.
What the Strong Mount does is allow the press to be set several inches further back onto the bench top, using a much larger footprint. This is a much more stable position and stance, which greatly reduces the amount of energy you need to exert to do the same job.
Yes, it will raise the height of the press by about 9-1/2 inches, but that is easily overcome by lowering the bench or raising your chair. If you already suffer from any type of shoulder or arm pain, or simply want to do more reloading with less effort, then positioning the press further back on the bench will REALLY help you.
Hope this explanation helps.