Pre-snap prowling only really makes a difference if the offense responds to it whether it's calling an audible or the QB sees the movement and decides the coverage is man when it's cover 2 in. So against the computer it's worthless, against another person it may make a difference, but then again if the only time the defense prowls like this is for this play, now I know it's 2 deep, four under and I know where my hot read is and where the hole in the zone is so this another play that without a complimentary play is pretty much useless.