
It sure is a component, or part of the serve. Unless you don't think the toss counts as part of the service motion either, in which I will disagree.
Consider this: using the countdown clock on the pro tour, the clock stops counting down when the player enters the beginning of his or her service motion (that is before the toss and well before any foot sliding). So the rules of the professional game consider everything that follows from that point (until they hit the ball) a part of the service motion.
Edit: All this talk of stances is actually irrelevant to
@oserver's point, because he doesn't have one!