It looks like his plan will decrease the mandibular plane angle by about 5 degrees. (You have a steep MP angle. Not a 'gonial' angle as you stated.) So, the plan includes CCW for that aspect.
However, since it is very steep, it will still be on the steep side even with an approx 5 degree decrease. The genio proposal will project out your chin but also elongate it such that it will look longer to you from frontal view so that even though the mandibular plane is made less steep via the CCW rotation to the maxilla, it won't look less steep in frontal due to the vertical displacement of the chin. It looks like type of genio where they would need to put some kind of bone buttress between the cut. It's not the type where the chin is slid onto itself or at least the diagram does not show that.
The BSSO in the proposal will pronounce out the jaw as to 'elongate it' but along an angle that will still be steep even when made about 5 degrees less steep by the CCW. It's not going elongate the ramus or give the posterior angle of the jaw a 'drop down'.
It clearly gives some profile improvement. But if you are doing it expecting to have the jaw 'look' of a model or Brad pitt from the front, it won't do that. So, it depends on your motivation for getting it. Your upper view certainly would be considered good looking. Maybe post the whole face, front and profile for more feedback and cross reference to the computer plan.