托古 or "attributing to the ancients" was a standard technique used by Chinese writers arguing for their positions, likely appealing to the tradition of ancestry

托古 or "attributing to the ancients" was a standard technique used by Chinese writers arguing for their positions, likely appealing to the tradition of ancestry worship. So we really can't take the claim of reverse engineering from the Zhou at its face value. It's more likely that the many schools of thoughts were original to the time, stimulated by the intense competition among the multitude of states.