Or the initial culture was stolen from there some time ago on a cotton swab.
Just because the DNA matches, it does not mean that was the source lab.
Have there been published reports of the DNA sigs of the other weaponized strains?
In this case it does; yes the strain existed naturally and went to USAMRID in the 1980's, but DOD Labs ARE THE ONLY SOURCE IN THE US OF WEAPONIZED AGENT-- this is not just the organic agent, it is the means of dispensing it. There are only four countries in the world that can weaponize agents, each process is unique, highly classified, and has its own chemical fingerprint; this one has been cited in numerous sources as having come from USAMRID-- hence the screening of employees who worked there such as Dr. Stephen Hatfield.