He took old photos and, using a computer, created animated sequences. An interesting idea. He got an idea to take still photos and put motion to them.
A gimmick, by definition, is a trick. I saw no trickery, just computer generated images.
They are artificial looking. Well, that could be because a computer generated them. I saw no indication that he was trying to pass off his work as real footage.
But, your reaction does raise a question. I wonder why he just didn't use colour film with sound, taken in the early 1900s and restore them?