Well, yes. He does have no idea what's going on, but she doesn't have to call him out on it. That's just adding salt to the wound, really. The seven months part of her statement is more startling, and Sherlock finds himself wishing the lights would come back on. Voices don't age, not the same way faces and expressions do-- not as noticeably, not as quickly. He wants verification, really wants answers, and most of all doesn't want to believe what she's said is true.

So he goes for the simplest answer. "It's a panopticon. Quite obviously, actually."