Here is a picture of my chin in what I feel is my normal position:
Yeah, you are way more deficient than I expected.
However, 10mm advancement of "maxilla" seems excessive to me. We don't know which part of the maxilla he's talking about, but assume it's upper incisor tip (this is best case, since everything else moves less). Even with 10mm of posterior downgrafting for CCW (this is a pretty large downgraft, so again, close to best case), you're still advancing A point 6mm or so.
In the case study you linked (
https://movahedoms.com/services/osa/case-study-1/), I think the guy would've looked better with less maxillary advancement. To me, his upper jaw looks protrusive, particularly in the 3/4 and profile shots, and his overall facial balance looks a bit off. In his case, I believe he traded off the best cosmetic outcome for a more functional outcome (larger advancement to treat sleep apnea). Of course, this tradeoff isn't necessarily bad, but if aesthetics are of high importance to you, I would try to avoid that much advancement.
I'd recommend a digital consult with Dr. Gunson (or other top docs) if you're concerned about the appearance part.