It is true you can muscle up and F-150 for a 2000 payload. The only person I talked to that had done so was pulling in the Rocky Mountains. He had no complaints about power but his unhitched gas mileage and ride comfort were miserable.
The fact is people have, do now and will in the future; exceed the TV Max cargo, the TT max tire speed limit, and a host of other things without the slightest problem. Their TT and TV combination and driving style has worked for them for years; so they are not about to tamper with it.
Other folks seem to have a disproportionate amount difficulty with seemingly suitable TV and TTs and end up adding or changing tires, suspensions and other peripherals. It is in these situations where the advice and suggestions from the board really shines.
The TV manufacturers give you the max cargo, max tongue and towing specs. The TT manufacturer gives you the TT specs. What they cannot tell you is how YOU will perceive your TT and TV handling.