The player can order subordinate units to interact (move to, get it, attack etc) with desired places/objects by pointing the mouse cursor/crosshair/centre of the screen at that place/object.
This behaviour is consistent, and can be generally used when looking through optics (including vehicle optics).
OBS:
When the player has their weapon deployed and is looking through optics, the mouse cursor becomes restricted to the X/Y (left/right) plane of the deployed weapon. All up/down motion is ignored, with the cursor moving vertically off the aimpoint/centre of the screen to remain fixed on the deployed weapon's X/Y plane.
EXP:
The mouse cursor should always behave in the same way, following the aimpoint/centre of the screen. This behaviour can be observed when looking through optics, while the weapon is not deployed. {F27822} {F27823}