Why are some Guru biographies, like those by Shri Dasganu Maharaj, considered less suitable for a focused Parayan?

The text explains in Chapter 0 that while the poetic works of Shri Dasganu Maharaj, such as Shri Bhaktalilamrut, are valuable, they are not ideal for a Parayan or Saptah focused on a single saint. This is because the biographies of individual saints within these collections are often not comprehensive or detailed, sometimes spanning only two or three pages. For a Parayan, which is an in-depth devotional reading, a more substantial, detailed, and comprehensive work is required to fully immerse the devotee in the saint's life and teachings, a quality the shorter biographies lack.