Simple empirical evidence. Have a friend jump in and saw back and forth on the steering wheel. You'll see it move, top side or bottom. I have my reservations about this brace, but my FF K-frame made huge strides in keeping everything solid.
I agree with you reinforcing the K Member will probably do better than this piece will. I am doing a Coil over Conversion right now with a Stock K and the mount that the steering box bolts to is only 3 way boxed from the factory with gaps etc between the metal and crappy welds. I will be 4 way boxing and re-welding just about every part of the K frame to eliminate its flexing just like the Firm Feel unit adding a tow hook to the front of it and a small skid plate.
I have some pictures of the K member, you can see the area of the steering box that I am referring to in these pictures here...
