I suspect they only tested this on google image search, which doesn't actually try to do any kind of fancy facial recognition - it just (I believe) drastically

I suspect they only tested this on google image search, which doesn't actually try to do any kind of fancy facial recognition - it just (I believe) drastically downsizes the image, and looks for images that are similar to the downsized image. So flipping the image 180 degrees would be good enough to "trick" google.