Quite easy when you know one is fake. Flagging fake articles in a review queue, by abstract only, and when none may exist all the way up to all being fake .... Now that's a challenge. Also, if you train GPT on the whole corpus of Nature / Science / whatever articles up to, say, 2005, could you feed it leading text about discoveries after 2005 and see if it hypothesizes the justification for those discoveries in the s…
I find the whole thing ominous because there is no "there" there: there is no understanding in the GPT-2 system, but it's able to generate increasingly plausible text. This greatly increases the amount of plausible nonsense that can be used to drown out actual research. You could certainly replace a lot of pop-sci and start several political movements with GPT-2... all of which has no actual nutritional content.
To what extent have our brains already decided what to say while we still perceive ourselves as 'thinking about the wording'?