>>13232586>the only way to pull that off would be if the adults told the children about those happeningsWhich is entirely possible. Just look at the amount of shit people make up online for attention, clout or just for the hell of it. It doesn't help that interviewing the children themselves is basically useless at best and counterproductive at worst.
I think in most cases the root might the parents uknowingly reinforcing and reifying a specific kind of game children sometimes engage in. When I was about 3 I used to love telling my mom about "when I was a grown up", fully aware that it was just a game. I'd make up an interesting adult self, often with her input. When we looked at old family photos we'd play at trying to "find me", because I liked to be included in everything my family did, even if it had happened before I was born. We'd usually settle on a random background person that shared my hair color or that looked young enough to not be a full adult being me, just hanging around before we were due to meet. Once again, at no moment did I think I was in any way in those pictures. However, I'm literally autistic (diagnosed) and I was never able to engage in many things kids often do (I never even had an imaginary friend), so these experiences might have been way more confusing, or had a totally different impact on a normal child. Imo, it's not a stretch to say an imaginative child would take similar games more seriously and start to build a story from there.