Why does the author in Chapter 50 find comparisons of Sai to the sun and moon to be insufficient?

In Chapter 50, the author, Hemadpant, concludes that metaphors involving the sun and moon are inadequate to capture Sai's true greatness. He reasons that it is "not fit to compare him to the sun, for that sun sets," implying a limitation and a period of absence. Similarly, he finds a comparison to the moon lacking because the moon "wanes," which signifies imperfection and cyclical change. As Chapter 50 clarifies, the fundamental reason these comparisons fail is that "Sai is forever complete." This highlights Sai's nature as being eternal, unchanging, and perfectly whole, transcending the transient and flawed characteristics of even the most powerful celestial bodies.