It’s a common English saying, “Is the X in the room with us right now”, implying that the other person is crazy or paranoid. Not specific to tankies or their apologists.
I know that, dude. I’m saying this specific instance of the phrase as it refers to tankies is being used often enough that it’s clearly a talking point. Its common usage by tankies to refer to tankies is way out of proportion to its prevalence in the English language. It’s a top-down mandated talking point, like “blue MAGA” or “genocide Joe”.