Well I finally found a write-up that shows pictures to explain the confusion about the axle shafts needing to engage the gear teeth.

http://www.offroaders.com/info/tech-corner/ez-locker.htm

It's not a Nissan application, it's for a Toyota, but the concept is identical. The factory side gears are re-used and the four-pinion journal is reused. I guess the issue with this setup is the obvious difference between the 2-pinion open carrier used on the 33-spline diffs.

I've been thinking even more about all the parts involved in doing hybrid swaps on these Nissan axles, and now I'd like to see if the new style 31-spline C200 axles will swap into an H233B. According to ARB's product guide, the 31-spline shafts are the same diameter between the old H233B and the new C200. I need to do more field research...