Why did Baba state that writing his life story was a pretext for Hemadpant to indulge his ego?

This appears to be a misunderstanding of Baba's words. In Chapter 2, Baba states that the author is "merely a pretext" because "I myself shall write my own story!" The condition for this divine assistance was not for the author to indulge his ego, but to completely dissolve it. Baba's words were, "He should dissolve his ego and surrender it at my feet. To one who acts thus in life, I give full assistance." When the ego is dissolved, Baba explained, "Then I myself shall enter with 'I-ness' and write with my own hand." So, the author being a pretext was conditional on the surrender of his ego, not the indulgence of it.