I think I was better than most kids at math, particularly algebra, but those kids grew up and caught up and I suspect many of them are as good or better at math than I am. I know nothing about child psychology or anything adjacent, but I honestly think a lot of "advanced child" stuff is just maturity.
My friend's child is profoundly gifted (160+ IQ). He is 12 years old and finishing Calculus and next year will be taking college math courses. His friends are a year younger than him and have qualified for AIME since they were 8 years old.
Giftedness is very real, and it's not just "maturity". Their brains are different. Seeing them squabble over math problems, it's like watching people talk a different language.