How does he know it never lags if he's never played online? If he's referring to single-player gameplay, then yeah, it doesn't lag. But that's the case with almost every gaming system these days anyway.
Lagging is a result of slow or poor interenet connection, so it depends from person to person. If you, or someone else you're playing with, has a bad connection, then yes, it will lag. Often times if you're slowing everyone down too much, you will be booted from the game so the rest of the players can continue without the game being so glitchy.