Where are you getting the part time and full time part??
Here's my take on this generic idea... (and I'm no XJ guy)
Full time 4wd means the front driveshaft
always spins.
Part time 4wd means the front driveshaft will not spin in 2wd (usually accompanied by lockouts)
You can have one or the other... not both.. but there are also wacky things like a tcase locking device that will force a 50/50 split of power front/rear.... guess I'm still confused on where you're getting the idea that it has both...