Attack move on cursor only works if you click RIGHT NEXT to the target!

Easily tested in the practice tool, if you have two dummies, one right in front of your champion (ranged) and one farther away, the attack move on cursor will only work on the farther one if you click right beside it. if you click farther behind the farthest dummy (indicating the farthest dummy is still closest to the mouse cursor) then you will auto the closest dummy to your champion. Why is this!?