What is the deeper meaning or symbolism of Sandy's tale about the soothsayer in Chapter 15 of The Westing Game?

“Okay, let’s see. Once, long ago in the olden days, there was this soothsayer who predicted the day of his own death. That day came, and the soothsayer waited to die and waited some more, but nothing happened. He was so surprised and so happy to be alive that he laughed and laughed. Then, at one minute to midnight, he suddenly died. He died laughing.” “He died laughing,” Turtle repeated thoughtfully. “That’s profound, Sandy. That’s very profound.”

To start, we have a lot of hints that Sandy is Mr. Westing.... in telling this story, he is virtually exposing his identity to Turtle and having great fun doing it. Sandy (Westing), in essence, is admitting he's alive..... Through the story of the soothsayer.... he tells his own.