What a funny post. I think its a predatory experience thing. I have snakes that will grab at an instant face, neck, body etc. then readjust after constricting them on the other hand my 11 year old bush baby girl is the perfect opportunistic predator and will wait sometimes hours for the single strike perfect grab and after constricting simply continue her grab to a swallow, rarely readjusting - I think it comes with experience and the snakes level of predatory skills.
LOL