I think it’s like a curve which falls off. Maturity. There are a bunch of individual things and lessons to learn which are part of being a Mature Adult. And the longer you’re alive, the more time you’ve had to be put in an experience where you must learn any one given lesson. So on average being older does make you more mature. But plenty of lessons slip through the cracks in otherwise mature people or happen to get taught to a person particularly early. And plenty of people don’t learn lessons at the same rate as others and remain broadly immature for longer, and in yhe same way plenty of people happen to learn lessons at a faster rate and therefore mature faster.
So half-mature teenagers, even when equally mature, are all half-mature in different ways. Like everybody has a different specialisation in the skill tree. And kids also have a skill tree, but they’ve had less time to put in points overall so they appear less specialised, and older adults have had more time to put points into everything and become decently well-rounded. Teenagers are very extreme. At least from what I see from inside
