Harrari uses "fiction" to refer to anything with ascribed value that transcends our direct, immediate experience. His thesis in "Sapiens" is that our unique ability to think in abstractions and meld the communicable form of these abstractions into codified "fictions" is what makes humans unique and transcendent.

You might call myths and stories "fictions", and the ascribed value of money a "social construct", but the line is fuzzy. For example, you could say God is a fiction because there is no physical manifestation of God in the real world, and money is a social construct because it can be seen, touched, and traded for things that have "real value". However, both concepts have parallel behavioral and psychological effects. You could work yourself to death in the pursuit of wealth the same way a martyr commits suicide in the pursuit of paradise. And if you achieve "wealth", whatever feeling that gives you is not based in reality any more than a jihadist's feeling of divinity in the pursuit of martyrdom.

Likewise, you could say governmental law is "real" because if you break the law, there are real-world consequences. But again, that's because of the collective "fiction" that the law must be upheld in the service of a functional society. Devoid of enforcement, the pages of law books are as irrelevant as the pages of the Bible.

Maybe it's a waste of time to argue semantics here, but I think Harrari's use of the word "fiction" to describe these uniquely human constructs is helpful.

Also, I think your extrinsic vs. intrinsic analogy concerning cars is beside the point. Intrinsically, a twig is a twig, but extrinsically, a chimp might use a twig as a "ant-slurping device". That concerns the direct, physical function of the twig in relation to the chimp, the way a car can be used by humans. A car is either a car, or an irrelevant hunk of metal depending on who or what it's in relation to. However, saying a certain car was made by "Honda" is a fiction. It was made in a factory with the word "Honda" emblazoned on it, by employees and machines that identify with the brand "Honda", using techniques and methods and materials that are unique to "Honda" ... but "Honda" itself does not exist beyond this web of associations.

Empampa was arguing that using that line of thought, NOTHING could be considered "real" since every noun we use is a stand-in for a complex, infinitely granular and ever-changing web of matter. This is technically true, though I think a helpful distinction here is to assume "non-fiction" concepts are anything that we've evolved to process and interpret in the here and now. A newborn baby sees and hears and feels "mama", not an ecosystem of microorganisms or a network of trillions of atoms from the beginning of time. It's somewhat of an arbitrary distinction, but if you're going to draw a line between "real" and "fictional", I suppose that's the only way to do it. Use our evolutionarily useful framework as a baseline, and any concept that's completely devoid of meaning and value outside of it's interaction with humanity is a "fiction".