So, is there any possibility there was an error with the two different rolls being processed in the same facility, and the person who took the photo of the figure is the one who disseminated the image? (getting an unexpected family portrait in their experimental art photography?)
Or can it only have been deliberately manipulated?
Two rolls of film somehow getting intermingled without anyone noticing, and then creating this well-composed image, seems pushing the bounds of possibility.
I think a modern digital manipulation is by far the most likely explanation.