According to the preface, why were some older biographies of Maharashtrian saints considered unsuitable for dedicated Parayans or Saptahs?

According to the details provided in Chapter 0, the biographies of Maharashtrian saints written by famous poets like Shri Mahipati and Shri Dasganu Maharaj were not considered ideal for a Parayan or Saptah dedicated to a single saint. The reason cited is that these biographies, found in works like Shri Bhaktalilamrut, were not comprehensive or detailed. They were often very brief, sometimes taking up only two or three pages. This lack of depth made them unsuitable for the focused, extended devotional study that a Parayan or Saptah requires, which led to the creation of more detailed works like the Shri Sai Satcharita.