We assume, like sauropods, that stegosaurs are relatively slow moving, and the phrase "sauropod-mimic" is being freely used, so maybe, just maybe, this particular stegosaur was doing just that. Not moving very much but being able to cover a lot more ground whilst eating, moving the long neck in an arc, maximising the energy intake without moving very much. Just a thought.
But is it even the case that holding the neck far out and moving it around costs less energy than walking a step?