I recently came up with this cast when I wanted a faster the way to do the poke so that my bulky heavy fly does not get a chance to sink too deep before the forward delivery. The inspiration for this cast came from the Tongariro Roll Cast and the Snap-T.
In lake fishing, some of the bulky baitfish pattern that I was using simply proved too challenging to extract from the water once they are sunk more than a few inches below the surface. Instead of using a heavier setup, I find that as long as I can get the fly to stay very near the surface before the forward cast, I will have no problem casting them.... hence a faster poke is born. The snap move allows the poke to be perform almost simultaneously with the pull back stroke. This cuts the time of the poke almost in half. The Snap Poke is typically performed after a roll cast to surface the fly.