Notice what's missing here? The script goes directly to the storyboarder. No nosey, interfering director to get in the way. What on Earth could a director contribute anyway? The advice to writers, "...nothing is left to the imagination of others", says it all. The director is one of those pesky "others."
I don't mean to say that the author wants to dispense with directors. My guess is that the director was omitted simply because the modern director's role is too unimportant to list in a short summary (obviously this doesn't hold for artist/creator-driven shows at places like Cartoon Network).