The defense industry is a mammoth thing. Not everyone is going to see all of it, but "staff engineers" have been a thing in the military for like 150 years now. The staff descriptor just means they're specialists in some technical field like civil engineering or medicine that provide guidance and solve problems. The modern tech definition hasn't drifted very far.
We should rename all the accountants "staff" though.
We should rename all the accountants "staff" though.