Sick details Dom. I've been hitting this recently but had no clue why it worked. The things you mentioned about stacking and foot positioning are money.
I really like this. I do BJJ mostly for self defense, and getting stuck in 50/50 or any leg tangle is really bad, because it leaves their hands free to go for weapons. So I really don't train leg or foot locks, I want to fight up and get hand control ASAP.
that detail of the foot turning underneath his back will prevent the footlock ya? I keep having an opponent wrapping there arm around my lead foot and attacking the footlock.
Don't use this pass in no gi. The turning of the heel that makes it effective is the same angle they need for the heel hook. Heel hook defense would require rotation of the foot in the opposite direction shown. For no gi I recommend turning the toes AWAY from the body and stacking the opponents 50/50 to clear your knee line and use a knee wedge with your other leg to finish your escape.