Exactly mandate, maturity doesn't shows only in physical appearance as most people think. To be matured means you're ready to face life, its risk and ready to take actions yourself. Just like you said, I've seen so many people who are grown enough to act matured but they're now. Like yesterday evening, a car broke down along our area, i helped the man fix the car, after that he couldn't say thank you for what i did. Is that maturity? Off course no, even when he's old enough to act matured by showing gratitude, he couldn't. So you're right about maturity.