If the image target scale has been set to real size (for reference, we have set namecard and idback target to real scale in the samples), then everything in the 3D scene is in real size. The distance of two objects in the 3D scene would be the distance in the real world.
A little more: In worldRoot center condition, MotionTracking moves the camera relative to the worldRoot as if the camera moves in the real world; And ImageTracking moves ImageTarget relative to camera as if the image stay/move in the real world only if the scale is same as the object in the real world.