How does the author differentiate between writing about worldly gurus, multiple saints, and one's own Sadguru in terms of spiritual benefits?

In Chapter 0, the author presents a hierarchy of written service. Writing biographies of worldly gurus is described as a worldly service, limited by time and space and rooted in self-interest, therefore it does not yield spiritual fruits. Writing about many saints is considered a form of Guru service that does provide spiritual benefits, but it is described as partial or one-sided and ultimately insufficient for attaining the ultimate spiritual goal. The supreme form of service, which grants the fruit of salvation, is to write the biography of one's own Sadguru and devoutly study it, as this is considered the most certain path.