So hopefully now you can see why I was (and am) surprised. I don't think I've ever seen a single-player game give away 20 hours of game as a demo. I guess when you have a 200-hour game, that's OK :)
"Significant surprise" doesn't even cover it. I know this is going to sound like I'm hyping, but I swear this is just what happened: I was told what the surprise was, and I was legitimately taken aback to the point where I had to ask Jon if I understood him correctly.