The word "epiphenomenalogy" is rare. The actual theory seems like an academic remnant of the default belief that 'You can't just reduce everything to numbers, people are more than that.'

So your last point seems entirely wrong. Zombie World comes from the urge to justify religious dualism or say that it wasn't all wrong (not in essence). And the fact that someone had to take it this far shows how untenable dualism seems in a practical sense, to educated people.