Assuming that the mouse pointer is parallel to the display and that a light themes is used, the visual click zone is positioned below and to the right of the upper left corner.
E: correct content
E₂ (correction): The visual click zone should be more than 1 px², but it’s not misaligned.
I think I understand the pixel you are referring too, it may be diagonally adjacent to the click pixel.
I’m not sure I understand ‘why’ post OP suggests that should be the ‘correct’ click pixel?
A drop shadow implies that the object is floating above a plane. If you have an object floating above a plane, it would need to drop to the plane to interact with it, so the interaction point should be the tip of the shadow, not the tip of the cursor.
But the cursor ‘dropping’ wouldn’t move it to where the shadow is? The light source is not directly above the cursor so the shadow is offset.
Depending on the relative direction of the light and “camera”, the click point could vary. It wouldn’t be on the tip of the shadow unless the shadow was already directly below the tip of the pointer in line with the line of sight. More likely it would fall somewhere “between” the apparent position of shadow and pointer before clicking.