There is a legend that the Discworld, which is held up by four elephants standing on the back of a turtle swimming through space, was once held up by five elephants. For some reason, one of the elephants slipped or jumped or whatever, and ended up crashing into the disc back when there was no one around to here the boom and ask philosophical questions.
Did an elephant actually fall? Who cares! There are tons and tons of mineral deposits in the place where it fell. And like every mineral-rich place in the real world, the result is a hotly contested region.
It doesn’t matter if the metaphor is fact: what matters is the reality the metaphor reflects, and the beliefs that hold together that reality. Does it matter if a particular Biblical tale is literally true? No, because it’s as true as it needs to be to make people act.
But like all Terry Pratchett novels, the book is may be about interesting concepts but its wrapped in wacko characters and brilliant satire. There’s an officer of the law so obsessed with sugar cube theft that he drives gnomes, trolls, dwarves, and some humans to form a union. There’s a furious troll who was fined for parking himself illegally. There’s moments of hilarity, darkness, and sometimes even beauty.