You do. When closed the vane in your AFM presents a physical restriction to flow. This restriction forces air to pass through the unmetered chamber where the screw is. Because of this arrangement adjusting the screw will shift the vane's idle position, which means the screw can be used to indirectly adjust idle mixture and, in fact, that's what it's there for. As airflow increases and the vane opens there is less of a restriction and therefore the screw's position has much less effect on it.
It's why the screw's factory insertion depth for that particular engine is coded (stamped) right into the housing. Not that you should be playing with it
In the Karman used on turbo motors the screw has very little such impact for what should be obvious reasons and serves a different purpose, which is why you don't find the coding on that AFM.