I suspect that was deliberate. DoW is the preferred nomenclature but DoD is still technically correct.

The article is phrased in a way to imply that the author would rather the publication maintain independence. It is probably the last time she will be permitted to say "department of defense".

They're not. That's executive fiat. The actual name of the department changes if Congress says it does.

The Department of War is an “alternate title”. Department of Defense continues to be correct