Based on Chapter 48 of the Sai Satcharitra, what distinguishes a true Sadguru from other spiritual teachers?

Chapter 48 of the Shri Sai Satcharitra explains that a true Sadguru is distinguished by the possession of direct self-experience, not just verbal knowledge. While other teachers might explain the Vedas or Vedanta, control their breath, or give mantras, their knowledge is considered "verbally hollow" without personal experience. The text asserts that a Sadguru is one who is a "giver of direct, full experience" and has the authority to truly enlighten disciples. Simply having vast theoretical knowledge is not enough to be called a Sadguru by the wise.