If you have 800 lbs of payload, two 175 lb adults you now have 450 lbs left of payload for a trailer you are left with ~4500 lbs of tow capacity using 10% of that on the tongue. It's not just people either - anything in your vehicle lowers your payload (the physical hitch itself, pets, coolers, accessories, ect)
Lots of people just look at pure tow capacity but ignore tongue weight/payload capacity of what they are using to two.
Most common F-150 configurations are actually limited on their tow capacity by payload over their advertised raw tow capacity. My 2012 F-150 farm truck has 1400 lb payload, minus two people and the hitch you're at ~ 900 lbs left for tongue weight so ~ 9000 lb pull load or ~4t
The other thing people neglect to consider is just where they tow and WHAT they tow. There's a big difference between a flat utility trailer and a square cargo trailer.
I guess my point is numbers aren't everything.
Source: 20 years in the professional trucking industry
That said, looking at the numbers still makes some sense to get a rough understanding of the design space of these cars though. (And, well, the numbers I was replying to were confusing the heck out of me.)
(My source: German class BE driver's license = car with heavy trailers. You're limited to 0.75t trailer OR (car + trailer) ≤ 3.5t without that, in B. The E is a separate exam, both theoretical and practical. Aside from theory bits on how cars with trailers behave, you have to parallel park or T-turn a trailer to pass it.)
Now I'm really confused. My father's Citroën CX station wagon (built 1983) was rated to tow 1.5/1.7/1.8t depending on configuration (AFAIR 2.5l Diesel engine for 1.8t), and we regularly made use of that. Admittedly 2026 is not 1983, but a BMW 3 class (not X3) can also tow 1.8t. What's the point of the F150? I guess if you want to do tow 1.8t every day? I would expect that the max rating also be higher if the reliability/life is better...