Video of B&W Flex

There are different types of "self locking nuts". A Nylock nut which is what the B&W hitch uses suffers from a crease in the plastic after one use. This will reduce it's ability to resist loosening due to the plastic deformation. However the amount of tightening torque will not change since the plastic adds very little to the necessary amount. The amount of torque added by the plastic deforming on the first use is probably in the neighbor hood of 5 ft.lbs, around 7% of the total 80 ft.lbs. required by the U-bolt nuts. That probably drops to 3 ft.lbs. on re-use.

IOW you can reuse this nut without thread deformation due to overtightening, unless you willfully overtighten, or neglect to use a torque wrench.