All I have said is that we know that many trans adults describe knowing they were trans as a child.
We know that's what they say. But I'm sure you're as aware as the rest of us that backstories can be embroidered or even simply invented. We don't know if they really knew or believed that as children, since we can't really know what's going on inside their heads.
But let's assume for a moment that those claims are true.
A trans adult says they knew they were trans as a child. They grew up and became a trans adult.
Are we also to assume that the converse is true? That every child who "knows" they are trans will grow up to be a trans adult? Or will it turn out to be just a phase or social contagion for many of them? After all, there are many more trans children, proportionally, than there are trans adults. If we are to assume that it's not just a phase or social contagion, why aren't there many more trans adults coming out later in life and saying how they knew they were trans all along?
How do you explain the high numbers of trans-identifying girls compared to boys, particularly as teenagers? If these girls are 'really trans' (whatever that means, since I think we still don't have a definition), where are all the middle-aged women coming out as trans who felt the same as these girls when they were teenagers?