I did look at it, guess I see how they do not tighten. Do you ever have a hard time getting them off?
They don't tighten because the cutter cuts the "pull" end off to the point that it cannot be grasped, pulled and tightened. The only tightening comes from the growth of the leg within the loop, not from any influences on the outside of the loop. Checking them regularly allows for easy removal as you catch it before it reaches a point that removal would be difficult. I've never had any issue removing them safely.