Do you have a link to that case? Inverted-L you mean an IVRO? I hear that can improve gonial angles quite nicely as well as jaw angle.
In the beginning I placed a lot of faith in HA paste, since then this forum has beaten that down a lot. I'm almost willing to just try and go for as flat a mandibular plane as possible and get an implant if need be.
Euphoria posted it...it's in here somewhere. Insanely steep occlusional angle and open bite (I think) They guy had trimax
If you elongate the ramus in the vertical dimension then you will move the teeth apart, vertically. Rotating the mandible will move the back teeth down even more. However you look at it it will be tricky.
No matter what you do, even if you get DO + BSSO, you will still need paste to smooth things over. There is a Dr Y case where someone got implants because their jawline wasn't smooth after jaw surgery
I think it's all going to depend on the actual shape of the gonial angle and the the occlusional plane
Consider this schematic
In the first row, you have the 'ideal' jaw shape and the 'downward growth' shape where everything is very steep, but not short. The guy who got the trimax with IVRO was like this.
In the 2nd row, the pic on the right has short ramus and mandible, obtuse gonial angle. Even if you do this DO + BSSO thing, the gonial angle is still the same shape and there is going to be a discrepancy after rotation that you will need paste or an implant to cover. That's why you might be better doing the cut in the angle itself, and fill it with a graft
In the 3rd row, the plane and angle are good, but the ramus and the mandible is short. In this case you would get a good improvement
The 4th case, which I didnt draw, would be were the angle is OK, but the upper and lower planes are steep. In this case you could do a lefort with rotation and rotational, lengthening SSRO (it it was stable)