Isn't another hardware problem being ignored here? Pound-for-pound muscle fibers are just superior to what you can achieve with electric motors or pneumatics.
Take size, strength, precision, longevity, and speed. It's not hard to match or beat organic muscle fibers on one or two of these dimensions with an electrically driven system, but if it does, it's going to neglect other dimensions to such a degree as to put building a humanoid robot that achieves parity with a human completely out of reach.
You can slather as much AI as you want on top of inadequate hardware - it's not going to help.
Electric motors are significantly better at the requirement that matters: endurance.
Sure it takes a bigger motor to produce the same torque, but speed and precision are actually the strengths of electric motors. The fundamental problem with them is that reducers are not impact resistant and they have internal inertia, which is something muscles do not have. Another problem is building actuators with multiple degrees of freedom. The ideal configuration for legs is a ball joint, not two consecutive rotary joints.