Usually the elephant in a room is something very evident about which no one wants to discuss about

But everyone is discussing how AI will have ads, so it’s not an elephant in the room.

Yes. My post was a joke -- I was trying to make fun of GP's (to me, baffling) use of the phrase "elephant in the room" by proposing an unlikely explanation for why they seemed to get its meaning back-to-front.

(Thinking about it a bit more, I actually think that the phrase's meaning could have really gone that other way. Nothing in the phrase itself suggests that the elephant is being deliberately ignored -- we only learn that critical part "in the background" via culture. For comparison, the similarly structured "bull in a China shop" means exactly what you would expect, without any implied reversal.)