Completely unnecessary and you can only use the long axle in the MacNamara bolt operated diff lock, as the short axle has lengthened splines to operate the diff lock.
The only damage I have personally seen to these axles was caused by my brother. 2A LWB ex army with a 253 V8, standard gearbox and transfer case, MacNamara hypoid rear diff with 4.7:1 ratios and 36" Silverstone MT117 tires. The vehicle fell backwards off a 1 meter rock ledge on full noise in low 1st. This managed to break the locking axle between the side gear in the diff and the cross shaft, and twist the outer spline on both axles. I don't think it would be possible to generate those sort of loads with a 2.25 petrol and standardish sized tires.

