Can sliding genioplasty be done at a certain angle? (photos)

I am looking to get Sliding genioplasty done by the end of the year. So far I've seen results where the jawline is clearly more contoured, some vertically reshaped, some made more square or pointy, and even lips appearance. My question is: Can the surgeon do the sliding genioplasty at a certain angle (as close to 90*), or does it just push the chin forward (in a case where a lower third is downgrown due to recession, it wouldn't look very appealing) See my illustration example after