Lutheran Christology can be basically summarized as the idea that in the hypostatic union the divine attributes are are communicated to Christ's human nature. The Lutherans still maintained a distinction between the two natures of Christ, but they claimed that many of the divine attributes are immediately and directly possessed by the human nature at the incarnation. So, for example, omnipotence is communicated to Christ's human nature. Reformed theologians found this not only unacceptable, but nonsensical.
Omnipotence belongs to the essence of God. In other words, to be omnipotent is to be God. And God's essence cannot be divided. Theologians call this the 'simplicity of God', that is, he is not made up of different parts; and so his wisdom is his power, his power is his goodness, and so forth. Since God's essence cannot be divided, if omnipotence were communicated to Christ's human nature so would be every other attribute, including eternity and self-existence. The human nature would have become God, even though God cannot change or become anything. This would mean, of course, that Christ simply had no human nature.
...Reformed theologians rejected both views [Catholic and Lutheran] on the relation of the two natures. They did this because of an important logical and theological maxim, namely that the finite is not capable of the infinite, or the finite cannot comprehend the infinite. This maxim was not only true of Christ's two natures in his state of humiliation, but even in his state of exaltation. This meant, therefore, that Christ's human nature had limitations; it meant that Christ actually developed from infancy into manhood. It also meant that there was an actual—not pretended—movement from humiliation to exaltation at his resurrection. This is why Christ could say at one point in his ministry: 'But concerning that day and hour no one knows, not even the angels of heaven, nor the Son, but the Father only' (Matt. 24:36; cf. Luke 2:52).