May I ask more about this specifically? AKA what you asked of Dr. G/ the aspects he most closely focused on during the surgery (emphasis on advancement vs emphasis on balance)?
Personally, I think that (upper) midface augmentation whether it be modified L3 or orbital rim implants or any other modality should be addressed AFTER THE bimax surgery in a SEPARATE SURGERY when the bimax surgery will let you SEE the relative deficiency to the mid face and WHERE it is. Although you can be pretty confident that Gunson would do a good job on the CCW bimax and opening the airways and all, I would NOT extrapolate that his midface augmentation would balance a significant bi max advancement. That's because the HA 'paste' (actually granules) goes up to 3mm and/or could be isolated to 'easy' areas like malar prominence (zygoma) or paranasal but not to orbital rim whereas implants and mod L3s can get up to 5mm.
So, Gunson, although quite GOOD at the bimax could be operating on the principle that the patient does not want to 'wait and see' what needs to be done in a SEPARATE surgery after the bimax or that patient wants ALL at SAME TIME.
That said, I shall tell you that IF you MIGHT need a SIGNIFICANT midface augment after a SIGNIFICANT bimax advancement, you should consider a SEPARATE surgery later down the line, especially if it's something like 5mm to orbital rim. That is to say, Gunson can't augment with the HA to parts of midface to the extent he can do the bi-max advancement. Nothing to do with skill. Rather the MATERIAL does not lend itself to more than 3mm. Material is good if you can 'frost' a large surface area of upper midface with it. So you really need to determine if he's going to BROAD BASE the stuff (good) or isolate to small area like malar eminence of cheek bone.
Personally, I think it's quite OK to have a RELATIVELY recessive midface after a bimax advancement. Just like it's OK to have a nose that might need adjustment after bimax. Then you go to ANOTHER doctor who is well versed in correcting what needs be corrected after the bimax.