The Father did not walk this earth as the man Jesus Christ.
St Augustine and i know this, i hope you disagree with the author as well.
Jesus Christ is the Word made flesh, God Incarnate. J. I. Packer says that the greatest mystery of the Christian faith is not the resurrection of Christ or his miracles, but his blessed incarnation—“the plurality of persons in the unity of God, and the union of Godhead and manhood in the person of Jesus” (J. I. Packer, Knowing God [Downers Grove, IL: 1993, InterVarsity Press], 53). Packer further states, “But once the Incarnation is grasped as a reality … other difficulties will dissolve” (Knowing God, p. 54).
The author’s commentary is well-crafted and profoundly informative.
Your accusation of modalism rests solely upon the author’s use of one word (man) which granted, the author could have tailored in a more suitable way. However, when read in context it is clear that the author is not a modalist nor is she implying that St. Augustine is.
No man is perfect. All of us are prone to error....including the author...and including yourself. That said, Christian charity on one hand, understands that the author could have crafted that particular sentence better while on the other, does not cast stones.