The hitch is rated as labeled. AS long as proper fasteners were used. LOL.
The weight distribution hitch accepts a bigger ball, plus spring loaded bars which are also mounted to the trailer. Insert the hitch into your reciever, hitch up the trailer, attach the bars, crank up the tension to preload the bars. Increases the weight distribution.
I have a 1990 Chevy G30. Even with a 1ton, 454/T400 powertrain, the weight limit on my factory powertrain tow setup is only 5000 pounds. Why? The 3.42 rear end ratio.
GVWR plus the trailer must not exceed the combined GCVWR recommended by the factory. Other important factors come into play, such as cooling, suspension, brakes, trailer brake control. Your ratings will be unique to your type of setup.
Always maintain a margin of safety under the max is a good rule of thumb.