The bottom one is larger, has an extra piece of cheese, and less lettuce on the top left portion of it.
But yes.
You are both correct. It appears that in the image that I have shared of these McDonald's "Big Mac" and "Grand Big Mac" sandwiches, it is pretty much just a single burger that has been mirrored and then altered with photoshop. Furthermore the soda and french fries appear to be have manipulated with image editing software as well.