frustum is like perspective view except the fact that perspective view is always symmetric if you make frustum asymmetric it will show you same effect as in image 2. now what happened to the 2nd image is that it has more view volume to its left side as compared to the right side, so if the image is in the middle it will shift to the right. example as shown here image-frustum more view volume on right as compared to left so it will look like object is pushed towards left because right volume is now occupy more space.
if we change the camera position or where it sees then our object's symmetry changes. Just as if you move your head left or right on the x axis, your computer screen's symmetry will change.feel like bit skewed.