The expression rock, he says, he uses of Adam. This, he affirms, is Adam: The chief corner-stone become the head of the corner. For that in the head the substance is the formative brain from which the entire family is fashioned. (Ephesians 3:15) Whom, he says, I place as a rock at the foundations of Zion. Allegorizing, he says, he speaks of the creation of the man. The rock is interposed (within) the teeth, as Homer says, enclosure of teeth, that is, a wall and fortress, in which exists the inner man, who there has fallen from Adam, the primal man above. And he has been severed without hands to effect the division, and has been borne down into the image of oblivion, being earthly and clayish.
http://www.newadvent.org/fathers/050105.htm
This myth talks about a Primal Man who was imprisoned in the material world. This his prison was allegorized by the cranial dome, place of the brain.
To break the cranial dome was necessary to free the Primal Man imprisoned in it.
So the cross, planted on the Golgotha (i.e., on the skull) like a sword (cfr. Matthew 10:34), effectively performed that operation of liberation.
So this interpretation betrayes the fact that the evangelists drew from previous Gnostic Gentile myths the fundamental idea of the Jesus' death, even if the myth of Jesus was essentially jewish.