The answer to this depends on what shooting technique you follow. I use a form of maintained lead called Move, Mount, Shoot which allows me to see birds in plenty of time.
The only time I move my hand back in this fashion is when shooting a very fast overhead target when I might need to move the gun a little bit faster or allow me to swing the muzzles past the perpendicular.
If you shoot follow-through and call for a teal with the muzzle on, or just over, the top of the trap then this hand position will improve your view of the target and enable you to see it earlier.
With my technique, no part of the gun obscures the bird once it has left the trap and, because my muzzles address a point well out on its flight line, I can watch the target come all the way up under the barrels without interference.
Why not give both methods a go and see which one you prefer?