Thanks, this is helpful.
So the morph depicts the widening of the anterior mandible both horizontally & vertically (1) coupled with a reduction to lateral chin (2).
https://www.researchgate.net/figure/Schema-of-preoperative-3D-skull-modeling-For-3-dimensional-3D-correction-of-the-chin_fig1_253330877
This paper shows at least (1) if I'm not mistaken.
Also, how does the soft tissue adhere to the decreased volume of bone in the case of a reduction/ reshaping? Does it depend on age etc.
These spin off questions have nothing to do with the objective of the demonstration. The objective of the demonstration was to show how simple grammar school applications of geometry can be used to OBSERVE basic changes made on the morph, in particular to observe you did NOT widen the chin.
Something that SHOWS you in the most simple way possible that your morph did NOT relate to widening the chin should be enough for you to put that information together to CONCLUDE your morph doesn't relate to a T shape osteo to widen the chin. So pointless to engage in cross reference to an academic paper showing a T shape osteo that has nothing to do with what you did in the morph. You did not shorten the chin, widen it or lengthen it as was shown in the academic paper.
My analysis of your morph has NOTHING TO DO with a T shaped osteo of the chin which was the whole point of the demonstration. So, pointless to refer to an academic paper on T shaped osteo that has nothing to do with what you did on the morph.
The other question also has nothing to do with the objective of the demonstration. So pointless to ask about soft tissue adherence. The point of the demonstration was to show how one COULD OBSERVE changes they did in a morph LEST they apply the changes they did in a morph to the WRONG type of surgery. The objective of the demonstration was to try in the most simple way possible to get you to OBSERVE something that can be observed. A SHAPE from the lateral chin was removed and a SHAPE to the anterior mandible was added which is what resulted in the ARC constructed in your morph. Both shapes were CURVES. One removed below a straight (diagonal) line and one added below a straight diagonal line.
So try to observe simple things that are there to observe before venturing into more complex material (eg. demonstrations in academic papers) and attempting to use those to observe things that can be observed WITHOUT them. That's probably why you're always confused. Complex stuff will be beyond you in the absence of mastering the simple.