Novels are literally made-up stories. If they actually happened, they wouldn't be novels, they would be memoirs or history or something.
We do disagree on whether the purpose of novels is to entertain or to deliver what you call TRUTH. Now, to be as generous as possible to your point, some writers can distill a lifetime of wisdom and experience into a work of literature in a way that expresses some meaningful sense or generality about the human condition. How do we tell those people apart from the ones who fall short of that? I don't think you can tell them apart by just reading their work. You'd need to have enough of a base of reference to understand whether the literature you're evaluating actually matches up to human nature. In other words, you have to already have some understanding of the human condition before you can accurately judge whether a work of literature actually contains the TRUTH about the human condition.
It's true that putting yourself in extreme situations will teach you a lot about the human condition. It's also true that you might die learning. It's especially true that most people who have actually been in those situations will almost universally agree that if you weren't there and you didn't experience it yourself, you will never actually know. You can tell because they write about it in their memoirs sometimes.
Between the base-of-reference problem and the nothing-perfectly-matches-up-to-the-real-thing problem, I just think it's bizarrely hyperbolic to write in all-capital-letters that novels are the only path to the TRUTH. That's an absurd and unrealistic expectation. Based on what you said, it would certainly imply that the best way to get even more TRUTH would be to have someone spend their life locked in a room doing nothing but reading fiction, and then whatever fiction they wrote based on that would really be the TRUTH. But that's not really how it works at all; most good novelists actually have some interesting real-life base of reference.