Hey Tom,
Are you are talking about the back of the boat were the hull bottom stops short a few inches and then steps up before reaching the transom?
This creates a built in engine setback, helping performance. When a boat is on plane the hull pad acts like a fulcrum, Balancing the nose weight to the engine weight/power. By moving the engine farther back from this pad,this helps with bow lift and helps performance.
I know why you asked,They are a pain when you are trying to install transducers on the back, Because they have to be mounted on the step or you will lose the bottom when you get on plane and the transducer rises out of the water. A regular hull design can just have a jackplate installed to add setback and would be easier for mounting cool stuff!