These creed-like statements read like a metaphor for the development of the concept of god being man -
459 The Word became flesh to be our model of holiness ... On the mountain of the Transfiguration, the Father commands: "Listen to him!"75 Jesus is the model for the Beatitudes and the norm of the new law ...
460 The Word became flesh to make us "partakers of the divine nature":78 "For this is why the Word became man, and the Son of God became the Son of man: so that man, by entering into communion with the Word and thus receiving divine sonship, might become a son of God."79 "For the Son of God became man so that we might become God."80
461 Taking up St. John's expression, "The Word became flesh",82 the Church calls "Incarnation" the fact that the Son of God assumed a human nature in order to accomplish our salvation in it.
465 The first 'heresies' denied not so much Christ's divinity as his true humanity (Gnostic Docetism).
468 After the Council of Chalcedon, some made of Christ's human nature a kind of personal subject. Against them, the fifth ecumenical council, at Constantinople in 553, confessed that "there is but one hypostasis [or person], which is our Lord Jesus Christ, one of the Trinity."93
IV. HOW IS THE SON OF GOD MAN?
470 Because "human nature was assumed, not absorbed" ...
http://www.vatican.va/archive/ccc_css/archive/catechism/p122a3p1.htm
ie. it's like they describe how the narrative developed - "
to be our model".