This is quite possible. At the time of removing and replacing the half-shafts, I recall marking a "D" and "P" to distinguish between driver and passenger side, which still exist to this day. However, that doesn't mean that they didn't get mixed up before I marked them. I have a beer drinking buffoon of a friend who was present that day. Although I wont rule out the possibility that I just spaced out and installed the wrong side half-shaft. Just to recap the current configuration: I now have the original half shafts installed in their original position. The half shafts that I installed a last summer are on the workbench, and are the same length. The original half-shaft "telescopes" or extends further than the newer half-shaft, the one i pulled out last night.
Maybe the half shafts i used to replace the original ones were the same length, and wrong in the first place, in other words, two left side shafts.
This all makes quite a bit more sense now, as I look at the spare differential on the floor. I can see how the casing is not asymmetrical requiring one shaft to be longer than the other. Just to be specific, I'm talking about the half-shaft, not the spline/axle that should require a great amount of force to remove.