Herodotus, Plutarch, and Aurelius all lived thousands of years after the period discussed by the book.
And a considerable portion of the book is devoted to exploring the possibility of consciousness being something very different from what we imagine it to be, yes; something not necessarily required for civilization or law. Calling that "useless sophistry" isn't really proof otherwise, it's just dismissing the idea out of hand.
Hinduism is made of a large array of different traditions evolving together over thousands of years. The early texts do not have that "obsession with consciousness" (and this, also, is discussed extensively in the book). Buddhism, also, post-dates his proposed "bicameral" period by millenia.
Nobody thinks this explanation is true, just extremely interesting and worthy of discussion.