This is some high level analysis; I'm very far away from seeing "big picture" things like this. You may be right, I don't know, but I'm not sure how this "fact" could be that helpful when you're actually taking the test. Are inference questions usually given reference by saying (lines X-Y) say...?
I swear, i tried two RC texts that had "Inference Qs" at the end and the right answer addressed some random word in the end... Check out the superprep Science Passage 2000; the last question, "the author suggests...." Then, i don;t remember which PrepTest# it was, they were talking about caves and culture and it mentioned shamans in the end. THe last question had "shamans" as it correct answer,,
I don't know, i tried this pattern, and i am getting it correct. I am not saying that every last question will have this but honestly RC is not as tricky as it seems