Does "Worked outside the U.S." include a DOD civilian on official military orders that worked in Saudi Arabia for all of 2021 but 16 days?

Yes, you should check the box for "Worked outside the U.S." on the Let's check for uncommon situations screen after you enter your Form W-2. However, because your employer is the U.S. DOD, you will not be eligible for a Foreign Income Exclusion, and there would also not be any foreign taxes paid that would apply toward the Foreign Tax Credit.