I asked about a specific saint, but the text doesn't seem to mention them. Why does the book advocate for focusing on just one Sadguru instead of many different saints?

The text explains that while writing the biographies of many saints is a form of Guru service that yields spiritual fruits, it is considered a partial approach. The Preface, as detailed in Chapter 0, argues that the most certain and effective service for attaining salvation is to write the biography of one's own Sadguru. This focused approach, involving personal study, readings (Parayans), and weekly recitations (Saptahs) with unwavering devotion, is believed to be superior for attaining the ultimate spiritual goal, unlike compiling stories of many different saints.