Bad technique.
Only works on people with a stiff back of extremely low tolorance for discomfort.
1. You grab the hamstring just below the knee not the knee in this control.
You assume that a technique has to result in a tap to be effective, this sucks, even if you don't tap. Forces the guy to fight out, which is good as he is uncomfortable and burning more energy to do so, often leading to other opportunities as well.