I do think that if a photograph is as staged or constructed as many of Jeff Wall's are, than the person responsible for the staging and construction is the one responsible for the photograph.
I also think that Wall is not involved here in preparing an artistic creation that just happens to be recorded on film. He has a photographer's sense, and his creations are clearly made for the camera, and the resulting print or transparency. His knowledge of light and film is clearly extensive and, to my mind, often inspired.
I also doubt that there are many Jeff Wall photographs where he doesn't spend a significant time behind the camera, even if he relies on one of his (large and talented) staff to finally release the shutter.
By the way, your thumbnail is a bit of a challenge. I don't know whether this will be better: