Really, this is probably the 2478237th essay entitled "Artifice" that I have written, but this one follows up to the most recent one, so, II.
I'm going to break things down to the beginning and see what happens.
A photo reifies its subject. That is, basically, the only thing it does by itself, it bears witness to the realness of whatever the camera was pointed at. Everything else that happens with a photo is inside your head.
So if you want to make some statement, to say something, which relies on or is supported by the realness of something else, a photo is just the ticket.
This is where modern documentary photographers can run into trouble. Mathieu Asselin (in Monsanto) wishes to make real for us a certain train accident which resulted in a spill of chemicals, so he photographs the crossing of road and tracks where the accident occurred some decades before. This is largely pointless, because what he actually wishes to reify is not a piece of land, but rather the billowing clouds of toxic gas.
Absent the clouds of toxic gas to photograph, he's going to want some other approach. No matter what, we are going to have to imagine the derailed train, and the clouds, nobody can show them to us.
In this case he might have been better served by a map indicating, say, the site of the accident, nearby residences and population centers, maybe arrows indicating wind direction. It provides, arguably, no less of an anchor for us to imagine the clouds of gas. But, he is a photographer, so we got a photo.
In the same way, as Mike C remarked, the little plastic model of the airplane is not the point. Nobody really disputes the existence of the little plastic model one can build, and nobody is much interested in it. What we are interested in is the Spitfire Mk IIA because Battle of Britain! (which used Mk Is, I am being witty, see?) so, a photograph of the actual plane would be better, and perhaps best is a painting of the actual plane downing some German fighter plane in a bewildering hail of ack-ack.
The point of a piece of visual art, or at any rate the point I perceive, is to allow you to imagine some larger thing. It is to give you a hook, a kernel, a trapdoor, into something bigger.
In the documentary or vernacular mode, the key lies directly in front of the camera. There's grandma, smiling. Click. By testifying to the reality of grandma and her smile, we open the door most conveniently to the imagining of her joy. The camera is pointed at some moment and scene (or several of them) which summarize the whole thing; in looking at the pictures we mentally reconstitute the whole thing, albeit with flourishes.
When purposefully photographing artifice, the key has to be the object in front of the lens.
The luxury retailer wants you to buy a dress, or a watch, or a car. To persuade you in that direction, they seek to evoke an imagined lifestyle, with drama, ease, and pleasure. The object they're trying to sell you, they want you to imagine, is an integral part of that lifestyle, and so they photograph that in an evocative way. The dress serves the role of the Spitfire, decidedly not the role of a small plastic model of the plane.
To return to Monsanto the dress is the billowing cloud of toxic gas, the lifestyle is the entire train wreck and its aftermath. Asselin wants to sell us a dress by photographing a sewing machine.