The reply treats knowledge as an attribute of perfection, not merely an external relation between two independently existing subjects. The structure of one proposed relation cannot be made the essence of knowing.
Knowing one's own reality is distinct from requiring an external mental picture of another object. The second is not a condition for the first.
To affirm ignorance of one's own essence would entail deficiency, contradicting the prior affirmation of complete and nondependent divine knowledge.