Holding at full draw for a few seconds can lead to more accurate shooting, but it's not automatic, because you have to learn one additional skill, which is maintaining back tension during the hold. In that sense, it's a more difficult method of shooting than snap shooting. It's possible that your shooting may get worse, or possibly less consistent for a while, before it gets better, while you're learning to maintain your back tension during the hold time. At least, it did for me.