I have long thought that the ID of the flag in PA is what you also think it is due to the cavalry fight on the March to the Sea and Kilpatrick's report of that fight and who they fought against.
One thing I would like to add - there were some units on the AOT during the Atlanta Campaign that already had Charleston Depot flags with them. These would be Gist's Brigade (and one other - forget which one right off) and Mercer's Brigade - Gist having obtained theirs in April 1863. Mercer was part of WHT Walker's Division and when that division was broken up after the Battle of Atlanta, Mercer was sent to Cleburne's Division. They retained their CD flags until September 1864 when these were replaced with new Hardee pattern battle flags which they used for the rest of the war. The CD flags they gave up have not been located so far.
Gist's Brigade retained their CD flags into the Tennessee Campaign as did some of the units of the other brigade whose name I cannot recall. A couple were taken at Franklin and Nashville.