That is true that most members dont drive their truck 1''-2'' off the ground. However we typically do. Thats why we build them. They look better lower to the ground driving. But thats my opinion. If he is talking about pinion angle it really depends on a few things with his truck. The reason we would point pinion down a few degrees is to compensate for flex. The thing is that the major detail left out is that it should be one to three degrees pointed down from parallel to the transmission (or the front driveshaft on a two-piece driveline). What that means is the pinion could, under certain circumstances, point up. But you can see from the diagram that the pinion angle can certainly be more than three degrees to be set up right. (or the front driveshaft on a two-piece driveline). What that means is the pinion could, under certain circumstances, point up.
Here is a video you guys might like...Trav's truck that we did about 10 years ago