I don't often take my trucks over a road that requires or causes that kind of flex. The is always the argument that the manufacturer would design the test to suit their particular needs, and show their trucks strength. I am certain that Ford could design a response that would make the Chevy or the Dodge look incredibly inferior, too. Kind of like some knucklehead coming on the forums and claiming that you HAVE to use 300+ degree heat to clean a parking garage, and saying that anyone that says otherwise is an idiot.
Personally, I have been taught that a certain amount of flex is necessary for longer life. That is why you will see something taht is welded that will have a bead for three or four inches and then a similar space until the next weld.