Tow vehicle "tow rating" is seldom the limit reached first when applied to a travel trailer as they will have a significant tongue weight. If you were towing another vehicle (like a motorhome towing a car) then it would be different as there would be nearly zero tongue weight and "tow rating" would be the limiting factor.
A travel trailers "tongue weight" will usually deplete a tow vehicles "cargo capacity" before "tow capacity" is reached.
TT brochure weights (dry and tongue) are usually significantly understated.