No - it's not straightforward. How the light strikes, sensor imperfections, patterns unique to each camera body even, thermal noise. It's very very hard actually. It's one thing to doctor a finished image - it's another, in a forensic level really, to doctor a RAW file. You can make one which on its own is syntactically correct but which does not show all the telltale signs of being shot in actual hardware, no patterns or imperfections etc. This is trivial.

Next level is to make it look plausible on its own, with plausible imperfections. This is a bit more involved and tedious.

The really hard part is to make it look like it came from the exact same individual purported camera body the photographer allegedly used. This is really hard.

An analogy would perhaps be taking a picture of a room:

Now, build another room that would make the same picture. Make sure everything in the room is plausible yet renders exactly the same picture as the first room. (The room is the RAW file.)

Edit: (I'm not saying all the competitions have the time and know how to verify a RAW file.)