If writing biographies of many saints is considered a valid form of Guru service, why does the Satcharita seem to discourage it in favor of focusing on only one Sadguru?

This is an insightful question about the philosophy presented in the book's preface. Chapter 0 clarifies that writing the biographies of many saints is indeed a form of Guru service that 'yields spiritual fruits.' However, it does not discourage the practice as much as it presents a hierarchy of spiritual service. The text describes this broader biographical work as 'one-sided or partial' and states that it is 'difficult, or rather impossible, to attain the ultimate spiritual goal merely through their writing.' In contrast, as explained in Chapter 0, writing and repeatedly studying the biography of one's own Sadguru is presented as the 'best and most certain service' for attaining the fruit of salvation. The book advocates for focused, unwavering devotion as the most effective path.