Is every miracle of the Church written about in numerous hymns, commented on by numerous fathers, or detailed by our holy councils?
Further, she was not vested as a priest in his vision. Still, I do not doubt the symbolic significance of his vision. Again, I trust the discernment of generations of monks from this lavra AND their bishops over the scruples of internet experts.
Whether she is vested or not is almost beside the point. She is administering the Eucharist, something consistently and unwaveringly the privilege and duty of clergy.
A very large chunk of Orthodox hymnographic, patristic and hymnographic deposit is dedicated to the Mother of God. She is spoken of in the most fulsome terms, yet, in their wisdom, the sainted hymnographers, iconographers and Fathers have never spoken of her as a priest. Surely, such an important symbolic status for the Mother of God would have been proclaimed and extolled, in the same way that the many OT prefigurations that have found their fulfillment in her are in our hymns, prayers and icons, such as the Burning Bush, the East Gate, the Uncut Mountain, and many more.
Furthermore, the statement "He was crucified for us under Pontius Pilate" was added to the creed to indicate that the Crucifixion was not simply an allegorical or symbolic event, but one that occurred in a specific time and place. Similarly, the idea of saying that the Mother of God was a symbolic priest and minister of the Eucharist is, at best, just incorrect pious tradition. At worst, it's straddling the gnostic concepts of undercutting the reality of Christ's mission and the occurrences.