I think they mean “first homosexual regular television companion.” Jack Harkness is pan. Mike Yates and Ace McShane are bi (via Word of God and EU materials). And Oliver Harper is a Big Finish character (companion of the First Doctor).
Yeah, my understanding is the first FULL time tv companion who is gay.. And Jack wasn’t considered full time or some such rubbish… I took it as a marketing ploy, similar to the extremely overblown controversy over the Beauty and the Beast exclusive gay scene.