Tow/Haul is NOT an actual Tow/Haul. It is a Hill decent Mode. The Ford owners manual does a good job of telling you exactly what it does.
When activated it will change the shift points in the tranny and still allow OD. Also when you are traveling thru hills if you top a hill on the descent it will down shift to help maintain speed if you don't have your foot on the gas. If you lightly press the brake pedal it will get a bit more aggressive and down shift more. If you keep your foot on the brakes it will attempt to bring you down to a halt as fast as possible.
Now take all of that into consideration, that if you set the cruz at let's say 55mph and have the Tow/Haul on they will work together to attempt to keep you there not only up the hill but also down the hill. The system does work and is the next and only best thing you can have for a gasser except a GM motor and Alison tranny behind it. Which we all know are not being made anymore.