...in a specific region, in a specific time period, immediately before the economic and then societal crash of the eastern Mediterranean that changed culture in the region forever.
The hypothesis breaks down pretty hard when you realize he just kind of handwaves away people in the rest of the world not having any kind of abrupt cut-over in the styles of recorded literature that forms the backbone of his arguments.
The fact that overall of recorded history you can find instances of any sort of interaction with something that's felt to be a voice that's independent from one's own subjectivity is open-ended to the point that it can fit the literary and cultural history of basically any civilization on Earth.
What would be more impressive is some additional specificity, any sort of evolutionary mechanism, and any sort of supporting biological data. Otherwise the thing that is being described here isn't a theory, it's barely even vibes. This is to vibes what vibes are to coherently formed thoughts.