Well, to take a phrase from NREL, in its strictest sense I wasn't citing authority for strict definitions so much as showing how "continental US" is most commonly used, which agrees with Psyren, as i suspect you'd agree that the US military, Department of Defense, Department of State, and Department of Homeland Security (the most common organizations to use "OCONUS") are going to be more familiar among most people and have more usage of the phrase than NREL.
The Alaska occurrence is neat though! I think if I was going to travel OCONUS (choose your own C) I'd probably shoot for New Zealand in 2028.