I would say that Graham and the Honorable Kavanaugh took the LOAC class before the terminology change. Enemy combatants work for a state actor. A US citizen can’t be one in US custody especially if the US is a party. Unlawful/Illegal/Non-Privileged are all they can be because there is no right to fight against the US if you are a citizen.
When was the terminology change? I would assume judges especially those up for SCOTUS would keep abreast of such things?