"You need to use psychology (etc) to understand human behavior because there is no complete understanding of physics or biology" to accomplish that goal is exactly one of those tautological claims I was referring to earlier.
Why is it that biology and physics is insufficient to explain human behavior? You can't answer that question beyond attacking the question itself without invoking metaphysics, and there are pretty much no metaphysical claims you can make about human behavior that you can't also make about robot behavior.
> Why is it that biology and physics is insufficient to explain human behavior?
They're insufficient to explain human behavior to humans, which is the thing that matters here. You can't fit a complete physical description of your brain inside your brain.
Why is it that biology and physics is insufficient to explain human behavior? You can't answer that question beyond attacking the question itself without invoking metaphysics, and there are pretty much no metaphysical claims you can make about human behavior that you can't also make about robot behavior.