Full tt 27 days post surgery: is this necrosis or scabbing? (Photos)

Your question indicates you are most worried about requiring further surgery if the involved area is necrosis and not scabbing. While the photos seem to indicate that necrosis is the more likely diagnosis, I am encouraged at the progress you are making. The size of the affected area is much smaller in the most recent photos and no open areas are visible. Allowing this area to continue to heal and improve with time is the most prudent step. Discuss a backup plan with your surgeon if complete healing or an open area develops. In general, areas of limited necrosis can often be remedied with a minor surgical procedure and the cosmetic outcome should be excellent. I hope this has been helpful. Best regards.