The reason EY wrote an entire sequence on metaethics is precisely because without the rest of the preparation people such as you who lack all that context immediately veer off course and start believing that he's asserting the existence (or non-existence) of "objective" morality, or that morality is about humans because humans are best or any other standard philosophical confusion that people automatically come up with whenever they think about ethics.

Of course this is merely a communication issue. I'd love to see a more skilled writer present EY's metaethical theory in a shorter form that still correctly conveys the idea, but it seems to be very difficult (especially since even half the people who do read the sequence still come away thinking it's moral relativism or something).