The parables of Jesus are often confusing for interpreters. These stories are symbolic and the authors of the gospels often use the symbolism for their own literary purposes. In all likelihood these parables unfolded from how Jesus used them to how the evangelist used them.
That being said, does it bother you if someone today does the same thing to a parable as found in the gospels? For instance, does Augustine or Origen infusing the parable of the prodigal son with various meanings bother you? If so, why? If a parable could unfold from Jesus’ meaning to the authorial meaning why not once again for another interpreter?