What is the weak link for Chevy max tow ratings?

Just because they can rate them that high due to a standard that does not test braking down grades longer than a 1/4 mile does not mean they should. That is like giving a half ton a 17k tow rating just because it can pull that up a hill at a minimum of 35 mph yet do not test to see if it can keep the weight in check down the hill without burning up the brakes.