Two Ancient Christologies p. 103f

Take for instance his interpretation of the crucial text St Luke 2.52. As Bruce has shown, Cyril does not hesitate to speak of a physical, but will not go so far as to posit a moral and intellectual growth—according to Cyril the manhood of Jesus Christ is perfect in wisdom from the start. So for him, as for Athanasius, the growth of wisdom is real but apparent. It is the gradual manifestation of a wisdom already present, for “it would have been an unwonted and strange thing if, yet being an infant, He had made a demonstration of His wisdom worthy of God”—therefore:

expanding it gradually and in proportion to the age of the body and [in this gradual manner] making it manifest to all. He might be said to increase [in wisdom] very appropriately (Adv Nest. 3.4).

Or, the growth in wisdom is “simply a holding back or concealment of wisdom existing in perfection from the first, out of respect to the physical law, the growth being rather that of the habit of those who were wondering at this Person:

It was in a sense necessary that He adapt Himself to the custom of our nature, lest He should be reckoned something strange as man by those who saw Him, while His body advanced in growth He concealed Himself and appeared daily wiser to those who saw and heard Him; . . . because He was even wiser and more gracious in the esteem of beholders, He said to have grown in wisdom and grace, so that His growth is to be referred rather to the habit of those who wondered at His wisdom that to Himself.

Thus the principle that the manhood was allowed to go through its own laws is in effect, surrendered: instead, we have a moral and intellectual growth which is only in appearance.