Reviews: Regression Planning Networks

The paper shows results on planning problems. If I understand correctly, these problems can be solved exactly if appropriate state estimators are trained (to check on the state of different objects, such as, if the cabbage is cooked or is raw). Thus, to me it is not clear as to what is the role of learning in solving these problems? If the problem could be solved exactly using appropriate classical planners, why should learning be used here at all? The paper argues in its text that symbols need to be hand-defined in classical approaches, but as far as I understand, they have also been largely hand-crafted in the proposed learned approach.