Yes, it does matter. If the prop shaft can't turn, and one rear wheel can be manually rotated, the other wheel HAS TO turn in the opposite direction. This applies with a LSD or open differential. That's because the ring, or crown, gear can't turn -- it's engaged through the pinion gear to the fixed prop shaft.
With an intact V-LSD, turning one wheel manually with the prop shaft fixed will be much more difficult than trying the same at the front. At the front, one wheel can probably be turned fairly quickly, and if spun fast it will continue to turn for at least a 1/2 turn. But with V-LSD, as soon as your hand is off the wheel, it stops.
When the prop shaft is free to turn, the friction of the drive shaft etc is less than the friction of the viscous coupler seals inside the differential. The seals are able to drag the other axle in the same direction. because the crown gear can now rotate.
This "test" only confirms the likelihood the differential is V-LSD. It's based on the friction of the seals. If the seals are badly worn, the wheel can be spun more easily. But, if the seals are worn, it's likely the special fluid in the viscous coupler has probably leaked out and the coupler isn't working. Similarly, even if the seals appear to be intact, it's still possible for there to have been some mixing of fluids, rendering the coupler ineffective.
According to the Identification section of my 07 FSM, the differential is supposed to have a label on the side, however, it didn't. I also checked a number of others in my dealers service department and they were all the same -- no label.
