That's a good question. Although I haven't watched the videos, I did read the Law of War manual, and this is my take:

In 2020 they weren't an occupying power, so this particular clause did not apply. Their infiltrated attack was indeed an act of war, but Trump and white hats effectively gave them the victory at that time for strategic reasons. (Presumably because fighting at that time would have caused civil war, way more US citizen deaths, invited in NATO and UN troops, and produced a more difficult fight overall. Instead they used this time to wake people up to unify the country, cause political chaos in other troop-contributing countries, catch more infiltrators, traitors and cabal-global-evildoers, effectively reducing US citizen deaths and suffering). And they waited for this time* to take back the country under these new and more favorable conditions.

And that's probably also why congress sidestepped making either DC or Puerto Rico into a state, because that would've also been a permanent change and they could've been killed quicker. But now with constitutionally required elections approaching, they can't put it off any longer, and NCSWIC.

(* insert hopium, prayers, and more prayers.)