The fact that a minimal amount of construction is involved in all photography, eg selecting what to include in the frame, does not entail that all photographs are highly constructed. Some fashion shots are, but what is constructed has to exist to be photographed, which is not true of fiction.
Many photojournalists go to great lengths, sometimes losing their lives, to bring us images of what has actually happened, and value their reputations for honesty and objectivity, particularly now that computers make image-manipulation so easy. Their work should not be compared to fiction, despite some modish Post-Modernists. Photographs can be used as evidence in court, novels can't.
When we learn that Doisneau used models for the couple kissing photograph we are somewhat disappointed and disillusioned, especially when he claimed that you had to pay with your life, with your time, for the chance which gave you the great photograph. In this case, the deception is of little consequence; it is not photojournalism. Doisneau's image reflects general truths about France (and in this such images are closer to fiction, which also deals in general truths); couples do kiss more freely and people stare at each other more openly than in England.
Perhaps we should not be disappointed to learn that his most famous picture is a clever construction; after all, how much of his life would he have had to give up just waiting for a couple to stop and kiss conveniently right in front of him as he sat in a cafe (as the foreground shows, adding to the Parisian ambience)? We might also regard it as an act of discretion; real lovers should be seen, but not shot.