Mr Noisy
Coming in your ears.
has he just air locker on the front?
because the back wheel was stationary
The NSR wheel will have been spinning. In centre diff lock you will have always 1 wheel on each axle allowed to spin.
With axle lockers no wheels are allowed to spin, power is sent to wheels with and without grip. The problem with standard Diffs is that power is sent to wheels without grip, a serious side effect to an otherwise brilliant design!