Hi Eric in response to the posting of your photoraphs of the Angophora (Corymbia?) I whish to share my perspective.
1. Based on Shigo what you describe as callus tissue is in fact wound wood. When newly generated sapwood first forms at the margins of a wound triggered by a release of stem pressure via lost growth stresses about a wound. Then loosley packed parenchyma cells are released (callus) this material differentiates into wound wood as it ages (begins to age upon contact with the environment), what we see as concentric rings of wound wood is lignified tissue not callus (which is non lignified).
2.The problem I see with the pruning cut is -
A) large limb material removed from a tree will reduce its lifespan up to the order of decades, even if it is cut to the most recently generated trunk collar.
B) Judging by the greater portion of woundwood at the sides of the wound, I see the top and bottom of the cut as being flush. This is evidenced by the formation of a seam in the wound wood at the top end of the wound where the cut was too close to the branch bark ridge. Also the wound wood is not uniform in its development akin to Shigo's dougnut (see attached)
Based on my study of Shigo and Mattheck I question the educations we have had as arborists, much of the work of the fathers of arboriculture was not
well interpreted by the educators in the Arboricultural profession.
Mostly I believe because of a lack of attention to detail, a lack of contractual experience and I believe because Shigo and Mattheck have been judged as opposed to being interpreted.
On a more humble note arboriculture like all proffessions (human endeavor) is in a state of evolution, I for one am grateful for those who have trod the path before us.
My Utter regards to all - Cassian...
Callus paterns-Wound Wood formation after pruning.pdf