The depth of knowledge in this area is simply stunning. What benefit does this knowledge offer an instructor? It offers the same benefit that most knowledge offers--greater confidence and ability at predicting and controlling the events in our environment.
This is why most experienced instructors feel comfortable demonstrating stall entry and recovery in all types of conditions and configurations (departure stalls, accelerated stalls, etc.). The depth of their knowledge allows them to precisely understand the limits of both pilot and airplane. This concept also applies to every other subject in aviation that instructors regularly teach.
If you're teaching others to fly, you're also learning about all facets of flying on a deeper level. So make the most of the opportunity, even if you're just building time. These lessons will serve you well later in your aviation life.