I have pulled with our twin jaw for over 20 miles on freeway, and country roads and crossing RR track all in the same trip with the handle UNLOCKED :S !! 5er was still there no issues. Look at the picture below and you will understand why I trust this hitch. Even more after the release handle Modification.
Due to the location of the pivot pins for the jaws the harder you pull the tighter they close, Back to High School physics.

modification.
The handle modification to me is the best thing you can do to prevent any chance of the pin box hitting the release handle.
BEFORE!
AFTER!