10% is a common hitch wieght recommendation for a ball/pintle mount trailer. 15% is typical max %.
In Europe, typical HW minimum is 7-8%, boats sometimes 7-8 also.
Using a lower hw% is better for a max trailer you can pull, assuming rated for that amount or not. 15% of 650 is 975 lbs of HW for the same 6500 lb trailer. If a 5W, 20-25% is recommended, so1300-1625 lbs is needed for a 6500 lb trailer. Quite possibly the next chassis sized larger truck!
It comes down to a game of numbers, from multiple angles, deciding which numbers you really should follow, vs good idea to follow.
Marty