He is wrong. On older vehicles, 97-03, the lock up was at the diff. The front diff was totally disengaged from the driveshaft until put in 4x4. Wheels only had a CV joint, no hub. On the 04 up, lock up is done at the wheel by an IWE, Integrated Wheel End. The default for this is locked and when you start the engine, vacuum is sent to the hubs and they are disengaged until you put it in 4x4. With a limited slip in front, it may make turning a bit difficult as the wheels will have a more difficult time turning different rpms.