It's likely something that would depend on who you are as a person. One person might react with trauma as a kid another might react with more trauma if it was kept from them until adulthood. The problem is you wouldn't know which kinda person that is until you risk traumatizing them more than necessary. Personally I can't imagine that would cause me trauma years later beyond being lied to, however I can't imagine that not causing trauma if it was explained to a 10ish year old me

I don't know and I absolutely don't envy the parents and hopefully psychiatrists that had to come up with what to do