Is there a term for "Children that don't feel like children"? Is there an explanation?

I'm 21F, for a long time I've thought about my childhood and even though I've shared this with my family they always say I was just a normal kid.

I remember from the age of 4 having thoughts of "I should talk this way", or "I should say this", so people would think I was a kid. I was aware I was one, but the actions didn't align, they were always forced, never natural. Not forced by anyone though, my parents are great and always gave me enough attention and love.

For example, I'd answer to a question like "What did you do in school?" and if the response was "Woow that's so amazing!!" in the common way adults talk to children I'd think "She acts like she cares so I feel good", this is a thought I'd have very often when adults would communicate with me.

Another one is having "conversations" with other kids and answering in ways I knew they'd understand, making my answers maybe shorter and more simple, mimicking the way they'd play, run, scream. But none of it was for me, I just knew that's how kids should act. If it was for me I would've been just watching and seeing how everyone acted cause watching them was much more interesting that acting like one. If we played with dolls, I'd let my friend be the doll she liked and play whatever she wanted cause my thought was "She's the one enjoying this".

This didn't come from a place of feeling like I was above the other kids, I just assumed I had to fake being a kid until I learned, and that adults didn't really care to have conversations with me but were nice cause they would try to sound interested.

My mother has said maybe it was cause she never baby talked me and would talk to me like I was older. But still, kids behavior is not fake, playing, running around, saying nonsense, it's just natural even for the most serious kid, I felt like my childhood was an act and other people believed it.