I think you're right. I recall noticing that after I turned 12 my approach to situations was fundamentally adultlike... I don't think I've changed much cognitively since then either... Just the slow accretion of experience, etc.

I did learn how to be more self-actualized, etc. since then, since a good portion of even the best K-6 education constitutes obedience training... which I had to unlearn.