Ramalito,
Jaw surgery as in 'maxfax' just to decrease either the steepness of the mandibular plane and/or increase the jaw to jaw distance is not the best option because it's not a 'given' that it will decrease the steepness as much as you would like or increase the jaw to jaw distance as much as you would like.
Whether or not HA augmentation done DURING a surgery, would be 'same/similar' as that of an implant would depend on whether or not the implant you would need was actually WITHIN the LIMITATIONS of what HA augmentation could achieve. In general, HA augmentation is limited to being on the MODEST side whether it be HA 'paste' (mainly for filling in DENTS) or HA 'granules' (HA mixed with COLLAGEN). The latter being the type know docs CONVERSANT in HA augmentation use such as Gunson and Mendelson who's RS link of a patient you gave. So, both of those doctors are quite responsible as to reserve HA augmentation to appropriate candidates who are indeed within the realm of MODEST augmentation with those materials. 'Sloppy or lumpy' looks are associated with use of HA augmentation basically EXCEEDING the LIMITATIONS of what it can do. Basically, when docs use the HA PASTE meant for filling in dents and dingies and use it to AUGMENT where the augmentation is meant to be MORE than 'modest'.
As to what HA augmentation could NOT do, whether it be 'paste' or 'granules' would be that it would not give you a WIDE jaw to jaw distance (IF you actually needed that.). It would not give you a 'drop down' to the back of your jaw either because the material is meant to be an OVERLAY and not something to extend a deficient area DOWNWARD.
HA augmentation with HA GRANULES is good for modest augmentations and the 2 doctors you have mentioned would be responsible enough to tell you if your goals were within the limitations of what the material could do. To the best of my knowledge, Gunson puts in DURING main maxfax surgery (but not as sole procedure). But other doc puts as a sole procedure.
That said, you can't rule them out based on someone 'imagining' them to be subpar and/or because he/she may have seen poor results when HA paste was used irresponsibly in act of exceeding what the material can actually do. But if you want to rule them in, you need to determine whether or not you are actually a candidate for MODEST augmentation with them. One way would be to consult with the doctors you came across who do them.
As to why HA augmentation is not more 'COMMON', it would be because it's often not a stand alone procedure and done when a maxfax surgery is also done and/OR when it is done AS a stand alone procedure, it is reserved for MODEST augmentations.
Jaw implants are more 'COMMON' because they are often associated with SIGNIFICANT augmentations where the aim is to 'drop down' as to extend the back of the jaw DOWNWARD and to also increase the jaw to jaw distance.
