There are other ways to manipulate images digitally, including flipping ore merging plates, that can affect perception. I know several people, even if they like a particular scene in a film, they still can pick up on the slight alterations. I've heard one person describe it as sterile, where there feels like there is no life to the actors, or the scene, or that they are manipulated in some way. There's something off to some people, similar to the uncanny valley.
So even if it isn't modeling or layering, there are people out there who can pick up on the changes done digitally.