What is telling about this example is that what seemed to have made the biggest impression was the least rehearsed, thought out, planned answer he could give, but rather the one that was the most sincere and most "down to earth."

I think there is so much about the YC format which really hints at that strategy likely being your best route of success -- the time constraint, the lack of pitch deck, etc. I mean, these are people who quite literally go through thousands of these. I can't really see any other way to possibly stand out than to try to be radically genuine and sincere, even when that seems (as the author seemed to have thought!) that it is the "less fancy" or "not the thing you are supposed to say." Quite literally anything else will be something they will have heard, at a minimum, dozens of other times.