Your presumption tells us it is NOT posterior downgrafting but rather a type of down grafting to show more upper teeth.
I will make some assumptions here too and draw my conclusions from them. In that way, YOU will know if my assumptions are correct in order to compare them to my conclusions.
ASSUMPTIONS:
I'm assuming your major complaint was NOT lack of tooth show and that you did NOT go in there saying something like: 'When I smile, NONE of my upper teeth show'.
I'm assuming your major complaint was NOT lower border asymmetry of the mandible NOR any canting of the maxilla. Basically that the asymmetry there was NOT a major issue for you.
I'm assuming BASICALLY, that lack of upper teeth show and canting of the maxilla and also canting of the mandible were NOT your MAJOR complaints when you consulted with him.
CONCLUSIONS:
The extent of a down graft to the maxilla whether it be an entire one to the whole of it or just an anterior down graft where BOTH could be used for MORE TOOTH SHOW, can only be as much as the LACK of tooth show. So if YOU did not go in there with major complaint of lack of tooth show and HE brought THAT to your attention, this 'lack of tooth show' would be MINOR and therefore MUCH LESS than that would be needed to distribute your soft tissue so your face looked MUCH LESS round to you. So, if the lack of tooth show was INSIGNIFICANT enough for YOU not to notice it or even have it as a complaint, the amount of 'extra face space' to distribute your soft tissues so all looks SIGNIFICANTLY LESS round to you will be as INSIGNIFICANT as the lack of tooth show you never noticed.
Usually, when a doc wants to cant the maxilla, it's because it's the maxilla cant that's responsible for some canting to the mandible. So canting of JUST ONE is all that is needed. So, his canting of the maxilla does NOT auto fix any cant to the mandible and just results in his needing to ALSO cant the mandible BECAUSE he cants the maxilla and all this is just going to result in some MINOR advancement of the lowerjaw.
Hence, I would conclude this surgery was being proposed to you based on HIS objectives where he may have found some 'employment opportunities' in your face that were NOT your MAJOR CONCERNS.
Therefore, IMO, you would be getting a surgery to address HIS findings which are MINOR and this surgery would tend to do very little for you with reference to YOUR reasons for getting it.
In terms of the major differences in opinion of Alfaro and him. They both see 'BACCALA'.
Alfaro, sets you straight and the other one looks for employment opportunities for himself.