Many readers based their speculations on the fact that a truly skilled manipulator can speak nothing but literal truths while still lying through their teeth. This is a thing that the faeries in the popular Dresden Files book series have down to an art form.
After today's comic, however, I don't think it's a spoiler to say that that's not what's happening here. This guy's just lying through his teeth to someone who believes he's incapable of it.
On a more technical note, figuring out the angles for this scene is a bit nightmarish for me. You've got the big but low to the ground Tara, floating Elliot, standing Ashley, and the glowing tall immortal floating even higher, and they've all got to be addressing and looking at one another. I like the results, but getting there was challenging.