Read it again, Dajjal. The Archdeacon speaks of the wound with a flow of blood and water... The Image of Edessa was understood to be ONLY a disembodied face on a cloth.
Another quotation from the Archdeacon's sermon:
"By the simple touching to the face of Christ, an image of his form was made, so that people would not think in a dangerous or perilous way that it never actually existed and has been invented."
Notice that the Archbishop believed the mere touching of his face resulted in the creation of an image of his FORM, not FACE, was made. In Greek, form and face are two completely different concepts... and this learned man did not make a mistake of definition... he uses the same word twice to indicate what is on the cloth. He tells us that the Image of Edessa is more than just a "disembodied" face on a small cloth, but an image of a form, implying much more.
Again, from the sermon:
"You wiped clean the sweat of the nature you had taken on and what was wiped clean was transformed into an image of your unchanging form, just like Adam's form was drawn out of the ground, like the eyes of nature in the folds of the kneaded earth."
Here we see the Archdeacon comparing the image of a "form" on the linen with the creation of Adam's body, his form not just his face, made from dust.
Further on we hear from the Archdeacon:
"For these are the beauties that have made up the true imprint of Christ, since after the drops fell, it was embellished by drops from his own side. Both are highly instructive – blood and water there, here sweat and image. Oh equality of happenings, since both have their origin in the same person. The source of living water can be seen and it gives us water, showing us that the origin of the image made by sweat is in fact of the same nature as the origin of that which makes the liquid flow from the side."
These are not mere metaphor or hyperbole but rather straighforward descriptions of what he sees on the cloth and his establishing an identity with the cloth's image and the dogma of the church.
"And for the prototype to be transferred to the likeness, he does this himself with the sweat of the human form he deigned to bear. . ."
Each time, when the Archdeacon refers to the image, he refers to the "form" rather than to the "face". "Face" is only used when he explains the myth of the formation of the image that was accepted for the Image of Edessa. He tells us the rest of the form was formed merely by the pressing of the face to the cloth. He also hints about something others have noticed... that the face has more detail and more definition than the other parts of the shroud.
"And best of all, honouring the top part of my body – for the most beautiful part is the face, not that which is below the armpits – I attribute the light shining out not to my own face but rather to the face of the one on the cloth".
The parenthetical aside in this quotation can be inferred to mean that there IS more image below the armpits.
Just after the Image of Edessa was transported to Constantinople, it disappeared from history... but a Holy Shroud appeared shortly thereafter in the inventories. It is a reasonable conclusion to make that the Image of Edessa was discovered to be more than a face and included the whole body.
In that the Archdeacon was describing the article that arrived in Constantinople, which was the Image of Edessa, you are correct, that is what the Archdeacon's sermon refers to.
However, the inclusion of the remarks on the side wound which has NEVER been associated with the Image of Edessa, the use of the Greek word for "form" when he refers to the image rather than "face," the reference to the creation of Adam's form (body) from dust, it is reasonable to conclude there is much more here than a mere facial portrait.