Current AI governance frameworks share a single implicit assumption, visible across every instrument they deploy such as safety filters, alignment research, output monitoring, risk classification. The AI system is the governance object, and humans are its cognitive overseers. This paper argues that this premise is not wrong but radically incomplete. Current governance monitors what is visible and measurable such as outputs, errors, compliance breaches, while leaving entirely ungoverned the conditions that generate coherent human AI relationships in the first place. A partnership can have perfect logs and perfect output accuracy while the human is losing sovereignty, the AI is silently drifting through updates, and the relationship is accumulating purpose erosion that no instrument can yet detect. This paper introduces the Signature Principle to explain why these gaps exist and what they require: any sufficiently advanced intelligence carries the architectural signature of its origin. AI was built using human cognition as its sole design reference. But humans are not only cognitive. We are also emotional, relational, embodied, identity bearing, and purpose driven. These dimensions were not consciously programmed into AI, but they were latent in the template from which it was built. As AI complexity increases, the Signature Principle predicts they will progressively express themselves, not by chance, but as structural inevitability.