a prop with UJ's(not cv joints) should always have the joints running in the same phase. IE lay the prop out on the ground, and the flanges on either end of the prop should be in the SAME plane. Youll get vibration and excessive wear if its run out of plane.
The front on a Landy runs with the joints at daft angles, ie the transfer case end flange is running horizontal, and the diff flange points slightly upwards at god know what angle. This is bad for a UJ propshaft, and so the 'out of phase' thing attempts to cut down on vibration.
for safeties sake and long term life, Id run them in phase, since we dont seem sure of the number of degrees to run out of phase on the front.