Workingonit,
The wobble in the unsupported end of the adapter shaft on the end of the ZF to LT230 allows for any slight misalignment in the axis of the ZF output shaft and that of the LT230. Although in the case of the LR use of the ZF with LT230 I suspect the primary reason for the use of the spud shaft is to make up for the difference in length of the gearbox output shaft((R380 vs ZF). The tolerance in the splines also allow for the misalignment as things can move with respect to each other e.g., the splines can slide as opposed to a a different coupling such as a bolted or taper (e.g., morse taper) joint.

