So it is a "limitation", just like any of the other "limitations", but exceeding the other "limitations" won't just reduce performance (and I'm the one getting the duhs here), but is strictly forbidden?
You will notice in none of the factory Ford ads, and pictures do you see a truck towing a big modern travel trailer or 5th wheel camper. They are always low profile horse trailers, contractor trailers, or mini excavators and such. I have heard on other forums Ford has denied warranty claims for exceeding the frontal aera limitation.
I personally think it is just like all the other recommendations, based on a worst case scenario that covers 99.9% of the idiot things people will do out there. A truck will hold 10 times the limit, or tow the space shuttle as in a famous Toyota ad. It then comes down to speed, road conditions, wind conditions, etc. Say for instance you can hit a 6" pothole at 60mph at max load, but a 12" pothole will brake the axle. On a nice, new smooth asphalt road you could load double or triple the weight and the axles will be fine. Same thing with tires, it is a load vs speed that causes failures. Less weight at 80 mph can be tougher on a tire then more weight at 50 mph, yet the truck tires have a on size fit's all weight rating that one can only assume is based on being good at the max speed rating which is say 110mph on the truck tires. So less then some insane 110mph fully loaded truck, you will be fine somewhat over but an normal speeds and we haven't even gotten into how air temperature effects them.
The new fancy tow tests are based on silly hot and maintaining a fast speed up a steep grade while running the A/C and such. Seems logical a truck may pull the load just fine if you don't have to be in such a hurry on the hills, or didn't live in the desert, or could live with rolling down the windows for a while instead of A/C. Don't get me wrong, I love them in that now at least all things are tested somewhat equal. The problem is you don't know what the limiting factor in the test was. If it was the braking then I would be unwilling to exceed, but if it was a heat problem I might be more willing to push things and just treat it more like a consideration like the frontal aera. If you are towing a 70 sqft frontal aera cargo box in the wind, it is different then a 70 sqft frontal aera Airstream camper (not that they make one but some 5ers are built with a great endcap, narrow TV gaps, and just the right taper for good aero drag considering their massive frontal aera.)
Anyway, sorry if I ruffled any feathers, I just like people to think for themselves and not just accept everything... even if it is a engineer saying it LOL!