The shaft is bolted to the steering box, no way for it to pull out causing a leak. There is a collaspable shaft between the box and steering coloum, the body lift extension bolts onto the end of the coloum. As you lift the body up the shaft will extend, Performance accessory must think that there is an unsafe amount of shaft engagment left that is why the need to the extension. Being said I have seen 3" lifts installed without the extension.
If your truck is leaking power steering fluid or hard to turn it has nothing to do with the body lift, look into the pump or steering box.