Hi Nigel,
Did not realize it was you. When I first saw the photo, I posted, I thought the same thing you did. This is a similar photo set up to about six of the Atlanta racers I have seen including Harry Glenn. They all look to have been taken in front of the same section, and may have been taken at the same time.
Jock's bike was described as a special, with the JAP engine coming in from England. The use of Indian forks, a handmade tank and frame, leads me to believe you're probably right. and this is Jock McNeil from Scotland on his JAP Special. It matches the special description in the Atlanta articles I've seen. Specials were often conglomerations of parts from different companies, like the bikes Maldwyn Jones raced over the years.
I think over the years the two McNeils have been merged into one. Because J.A. lived longer, and worked for several racing teams, he has been given credited for most of the accomplishments of both McNeils.
I went back and checked the Atlanta Constitution Articles on Jock's death in Atlanta. Apparently Jocks brother arrived in Atlanta on the Monday after his death. He had come down to see his brother race, and had not heard of his death. The article says his brother worked for the Indian Motorcycle Company in Springfield, MA. There is no mention in the Constitution of him being buried in Atlanta. I searched the online records for Atlanta Cemeteries, and couldn't find, but I suspect he's buried there.
You are probably also right about J.A. McNeils war injuries. I read that in a Bicycling Magazine article, which solicited readers to write him with well wishes. These articles often over, or under state injuries. I found one the other day, on another famous racer, who received "minor injuries" in a crash, which was actually a skull fracture.
Maybe someday, we will sort out the McNeils stories, but I think we're on the same page.