Why does the author of the Shri Sai Satcharitra find it inadequate to compare Sai to the sun and the moon in Chapter 50?

In Chapter 50 of the Shri Sai Satcharitra, the author, Hemad, explains why common celestial comparisons are insufficient for describing Sai Baba's true nature. He considers comparing Sai to the sun, but rejects it because 'that sun sets,' implying a period of absence or darkness which does not apply to the ever-present Sai. He then considers comparing Him to the moon, but finds this inadequate as well because the moon 'wanes' and is not always full. The chapter powerfully concludes this line of reasoning by stating that 'Sai is forever complete.' This illustrates that Sai's eternal, unchanging, and perfect essence transcends the cyclical and impermanent qualities of even the most glorious objects in the physical world.