Supose you have 4 points on a box. If you randomly increase or decrease the location of each point by some random value say +-3% then averaged 100,000 of those boxes, you get a smaller box(1) surrounded by a larger increasingly blurry box. This is true even if no single picture shows that single smaller box, but it will show up on the average.

(1) Rather than a true box the midpoints are going to be slightly buldging, but with a large sample set it's very close to a box.

Sure, you can get into cat and mouse games ever stranger geometry. But, the water mark is limited by how much it distracts from the image.