Yeah. There's pretty much been no hint whatsoever that Nagato can actually "revive" anyone yet the guy is already basing a theory about it. Rather the opposite. I think it was said that Yahiko was dead, but yet his body is there controlled by Nagato. So it pretty much doesn't let you think he can actually bring someone back from the dead.

He either took a peek at the manga, manga section, or was spoiled about something somewhere and has a vague idea of what's about to happen, just as Aizen planned.