Chukchi Husky
Lone Wolf
I don't think that has anything to do with it. The fact that a game contains linear-questions doesn't mean that the game is itself linear. That would only be the case if you had to advance through all quests in a predetermined manner, which isn't the case.
They said that doing quests in any order you like doesn't count as non linear, as there is still an ending to the story. I think the example they used was a Japanese RPG where there was four quests you could do in any order.
Further, what about games like Civilization, which don't have any sort of plot at all? Surely they prove that non-linear games can exist?
I don't think it counts as there's no plot. Even if it did, the game still has an ending, so it's still non-linear.