You are exactly right. Six year old children have no concept of sexuality and therefore cannot possibly know what their FUTURE sexual preference will be.
This “I’ve known since I was six”, i.e. “I was born this way”, is just one of those memes designed to shut the normal world up, so long as one doesn’t really think about it too much.
So let’s take this to it’s logical conclusion. It doesn’t matter if one was ‘born that way’. God knows that and He still said it’s a sin.
I was born pooping when and where I liked...