Maybe I'm missing something here, but ISTM the question isn't really whether the logs are of a genuine conversation about CP, but rather whether the accused really was a part of that conversation? After all, if he really took part in a conversation about procuring such material, it wouldn't have mattered if he talked like a newb. Likewise, if he wasn't in on it, it doesn't matter that everyone who was in on it got "the lingo" right.
ps. How would one know enough about the scene to motivate such skepticism?