Yes Danie, the final drive has its own separate oil supply from the swingarm/driveshaft. A common problem can occur where the seal on the input of the cardan drive starts to leak, and the result is usually the oil from the swingarm draining into the final drive, overfilling it -- but, it is also possible for the oil to go the other way.
I suspect that the moisture from your driveshaft/swingarm oil may be seeping in from the infamous rubber bellows that covers the universal joint between the transmission output and the swingarm. Water can seep in there if you do alot of riding in watery places, or cracks can form or the clamps aren't always water tight. Also, there is a hole in the bellows/boot which is supposed to be pointed DOWNWARD for water to drain - it can be a point of ingress as well.