I have one and judging by the video here
I would guess mine does what it is supposed to be doing, but it should be doing something else.
https://www.ministryofpinball.com claim the hand would be moving from "right to left", mine is merely shaking. And it does so in the rhythm of the right "start movie" controlled lamp matrix lamps. While I think it should really be connected to the creature mirror/arm and shake when you see the Creature light up.