What is the distinction made between writing the biography of a worldly figure versus that of a saint?

The preface in Chapter 0 draws a clear line between worldly and spiritual service. Writing the biographies of great worldly figures like politicians or historians is considered a worldly service. While it can be a form of public service, its importance and fruit are not eternal, being limited by space and time and often rooted in self-interest. Therefore, it does not yield spiritual fruits. In contrast, writing the biographies of saints is a form of Guru service that does yield spiritual fruits, although even this is described as a partial path to the ultimate goal.