Shouldn't all of the weight be on the goose ball in the bed. I would think the frame only sees some forces to keep the main adapter in place.
If an Andersen or the B&W Companion are torque down to the bed with the aid of the goose ball, then the ball can not be holding ANYTHING up. You can not pull down and push up at the same time, you get one or the other. ALL the weight is carried on the bed floor. It is torqued down to prevent it from turning on the floor and if it is turning then it is not torque down correctly, and should be re-torqued after the pin weight is added.
B&W added strips to fit the valleys in the bed floor because people were getting dents in the raised ridges of the bed floor. Realize that both the Andersen and Companion are compromise hitches that bypass the direct mounting to the trucks frame rails. With the compromise being less weight and easier to move around.
Way back in the beginning of 5th wheel hitches for RVs, the hitches were just bolted to the bed floor. Trailers have gotten much larger and heavier over the years and truck bed have gotten thinner and thinner metal.
The puck systems are giant leaps forward, my RAM puck system is very robust and I am sure the others are also. RAM has a plate welded on each side of the frame rail for each of the four puck locations. All new 2500 and 3500's come OEM with these plates. The option for the pucks in a bargain for $400, as it provides the 4 pucks, bed electrical and the gooseneck hitch. My RAM did not have the feature. I added just the electrical kit and four pucks for the same 400 bucks. Took 4 hours to install working by myself. The bed has to be raised one side at a time to drop the pucks in place. Then two large high grade bolts capture each puck between the plates.
Andersen does make a rail mounted version that pins to rails, and on a RAM the Demco 6099 picture frame that locks into the pucks will hold that version of the Andersen. However the Demco 6099 weight over 80 pound, so you are defeating the whole weight savings thingy.
Chris