With that type of lift, it has to be closer to the front of the vehicle. If it were centered, the weight of the engine and transmission would make it tip forward. These are simple lifts, that are much cheaper and have a lower insurance cost. A friend of mine has one, and that's how we use it with our trucks. With the cars it is more centered.
The Discount Tire I shop at, puts my truck on the same way, but they put a floor jack with a pad under the differential just to be safe. I have seen them put 2 jacks under the shock mount on trucks with custom differential covers.