>>473252372That's not it.. the only reason going into "3d mode" (crossing your eyes) works on those other images is because they're stereograms where one image is shown at a slightly different angle, so your brain is able to piece it together as three-dimensional. At least that's a simple explanation, I'm not sure what's happening like neurologically or whatever.
On that gif, since you're looking at the center and not at either of the pictures, you see the pictures in your peripherals, making them lack details. Because of that your brain starts to distort the images and they begin looking weird