I got it. Or rather, I didn't get half the references but I got enough to know exactly what was going on and understand the situation - i.e. that Sam thinks the crossword is feeding him abbreviations of medical stuff going on with his real body in a coma.

I think that it's hard to say whether the two people who didn't get it just didn't have enough information. Were they aware the entire show is about a man who thinks he's trapped in a coma and periodically gets odd messages from the "real" world? Because that's kind of a massive clue which I think would crystalise the issue. Certainly I'd be surprised if viewers of the show didn't "get" what was going on...