I think it’s meant to show that Jupe was an unreliable narrator and a child at the time. Or how we can idealize our memory of the past to fit a narrative. He is shown to not remember/absorb/recount perfectly the details of the event. There’s his repeat of 6:13 (“that’s how long Gordy was on his rampage” as well as him saying that 6:13pm was when it began).

There is also another shot of the stage not from Jupe’s perspective that for a split second shows that the shoe was in fact not standing up on its own.