My friend and I are planning on going out on some light trails this weekend. He has a 2000.5 model year QX4 with the electronic 4wd selector. He was perplexed over the concept of driving backwards to disengage the hubs, which is nothing new in the auto-hubs world or to me.

No manual available to us--anyone know if his machine still requires a reverse?

His QX4 has full-time hubs. No backing up required, as they cannot disengage, like the automatic hubs on the X.

All he needs to do is shift out of 4HI and into 2WD or "Auto".

Eeeenteresting...what is the advantage of that? Disadvantages?

Advantages:
Allow all-mode 4WD (basically AWD) to work as designed. In order for AWD systems to work, engine torque must be available to all wheels all the time, at any speed.
Don't require any backing up to "disengage"
Don't lock and unlock during directional changes like automatic hubs do
Are stronger than automatic hubs and probably many manual hubs as well.

Disadvantages:
Front drivetrain always rotates, whether engine torque is being sent through it or not. This contributes to possibly lower fuel economy and increased wear on the front drivetrain. Also, if a CV joint or boot is damaged while off-road, the vehicle must be flat-bed towed in order to fix it. Auto or manual hubs allow the front drivetrain to be physically disengaged from the wheels.