i think the main confusion here is not so much "non-linearity" but rather over the concept of "story". As we all know "story" is something that takes place in "the future" (or in the "presence"), it unfolds as we read or watch it. This is opposed to "history" which is something that took place in the past ("hi-" meaning "in the past"). So, when we are talking about a story we don't know how it will end simply because it's happening right now. A story is therefore by default "non-linear", while "history" is linear.
let it be known that I'm not much of a story-teller but I'm good enough to impress the s*** out of people at c***tail parties (I them attend frequently). I also hold an MBA from Wharton, something which has absolutely no bearing on a game forum, I simply like to tell people about it...