Undisclosed or non-obvious composites are the antithesis of photography.
I wouldn't say that, because I think it works better to understand "photography" as a very broad descriptive term, meaning something like "making images using a camera and post processing", and to separate out ethical considerations about what is done within that domain. Importing the ethical considerations into the definition of photography (as I think you are doing) seems to create misunderstanding and raised blood pressure. I agree, though, that transparency about post processing is sometimes essential, particularly where there are rules (competitions) and/or an expectation that the image will be in some sense "telling the truth" (documentary or press photography). Where there are no rules and no expectations (much "art photography") then transparency about the means may be interesting but certainly isn't mandatory, and it may even be legitimate for the artist/photographer to deliberately mislead the viewer, or at least play with the expectation (from which photography that looks as if it might represent something seen can't easily escape) that a certain kind of truth is being told. There are grey areas (some "landscape art photography") which give rise to heated debate. Is it enough for it to be beautiful, or does it have to show everything that was there? An issue we go over again and again on this site, and for good reason, IMO.