JK Rowling entendeu errado. Na verdade, ela estava certa, seu editor disse a ela que estava errado, e ela mudou para o jeito errado. Isso foi corrigido em versões posteriores.
A explicação estava previamente em seu site oficial , mas o site dela passou por um grande reabastecimento recentemente. De qualquer forma, rastreei a citação original e a incluímos abaixo.
At the end of 'Goblet of Fire', in which order should Harry's parents have come out of the wand?
Lily first, then James. That’s how it appears in my original manuscript but we were under enormous pressure to edit it very fast and my American editor thought that was the wrong way around, and he is so good at catching small errors I changed it without thinking, then realised it had been right in the first place. We were all very sleep-deprived at the time.