Wasn't Hemadpant, the author, a perfect and pious devotee from the very beginning?

No, the text portrays a very different initial character for the author. Chapter 2 explicitly states that before his transformation, the writer was "mischievous, talkative, cynical, and critical." He was arrogant about his own knowledge, had a logic-driven mind, and was prone to argumentation. The text further mentions that he was proud of his wisdom and initially "knew nothing of the Satguru's greatness." The story of how he received the name "Hemadpant," which is introduced in Chapter 2, serves to explain this background and his eventual spiritual development under Sai Baba's influence.