The article includes a video showing they were able to use FaceApp on the non-smiling photo to reproduce the smiling photo exactly. They also include analysis

The article includes a video showing they were able to use FaceApp on the non-smiling photo to reproduce the smiling photo exactly. They also include analysis comparing the smiling photo to other existing photos of those people smiling and note that in the smiling photo some people are depicted with dimples that the person doesn't actually have.