So keep saying it. We need to know who to avoid.
She wrote him as a believable (albeit magical) character. Real life people generally don’t work like this: “blah blah blah oh yeah I’m gay blah blah blah…
Do you know any straight couples? Did they have to tell you they were straight? No. But they introduce you to their significant others. They wear wedding rings. They have pictures of their families up at work (or on their computers/phones as wallpaper). They talk about their weekend plans, which include doing things with their partners (or looking for one).
The entire Harry Potter series is FULL of people who reveal that they’re straight (or at least in/looking for heterosexual relationships). Think about how weird and unrealistic it would be if Ron was still a character and his family was still there and Harry still stayed with them, but the book bent over backwards to hide everything that would make it explicitly clear that Molly is married to Arthur and they’ve had children together.
"Real people" who are straight have their orientations affirmed a thousand times a day. They reveal their own orientations casually without ever thinking about what they’re doing, because that’s what normalcy looks like to them.
"Real people" don’t live their lives in a way that obliterates every external trace of their sexual/romantic orientation.
Well, sometimes queer people do… when it’s not safe for us to do so. When we have to fear the consequences of being out.
So maybe the lesson is that the Wizarding World is homophobic? But even when they’re alone—and Dumbledore is dead—and even when the subject of Dumbledore’s past with Grindelwald (the man Rowling says he was in love with) comes up and Harry is basically begging him to explain himself, to reconcile how he can be the good man that Harry knew and do all this bad stuff, and Dumbledore doesn’t even say, “I was in love.”
Is that “realistic” to you?
They’re alone, Dumbledore can’t be hurt by anything any more, he’s unburdening himself of his last secrets, and he still holds back this last piece for no other reason except that this way there’s no canon gay in this book to alarm the kiddies’ parents.
Dumbledore’s youthful love was so critical to the plot, it’s part of the explanation for why Voldemort died in his last duel with Harry (because it explains how the elder wand’s chain of custody ran through Dumbledore). But it’s glossed over, not for story reasons or believability but because of a editorial/marketing decision rooted in homophobia. That’s not realism. That’s not believability. That’s not treating gay characters the same as everyone else.
What you’re saying—whether you realize it or not—is that for a gay character to be “believable”, they have to be so deeply closeted that it never comes up.
Try to defend that.