The Gen4 Jimny has an additional cross member added to the chassis below the prop shaft to give the chassis better rigidity. When lifting the Jimny by 50mm and adding castor correction bushes, the prop shaft moves closer to the cross member and this means that when you go over road humps at speed the two knock together briefly.
The Des Sol design allows for a notch directly in the line of the prop shaft, this prevents the two from touching. A stronger, more practical parts for your vehicle!