Others can decide for themselves........I'm not here to argue with an engineer.
But then.........
Start with the inherent flaws of the frame it's attached to then.
The premise of the test you performed is flawed because it does not look at the whole picture and over engineering one portion of a complex equation does not a problem solve.
Also look at gearing, horse power, weight distribution, weight of vehicle to weight of cargo/trailer, braking, trailer braking, transmission etc....
Whether it be Reese or DrawTite or any other manufacturer would have considered all these factors.
Also a ClassIV is a completely different animal........not anything like the ClassIII you are testing. ClassIV is chassis mounted in the bed much like a fifth-wheel but uses a 3" ball.
There is more here that some kind of Cad test program of one portion of the whole.