I completely disagree with you. Maturity depends on so many social, cultural, and biological factors that you cannot possibly put an age to it, or even measure it in general.
yeah some of it applies to me, when i was 15 i was very rebellious! i've kind of calmed down now so i can get good grades to go to uni, then the fun begins again bwahaha! when i was 3 i had a boyfriend! and apparently since i was a toddler i used to flirt with men haha. then i got pretty shy from like 9- 13ish. i think mentality varies from person to person :]
I think I was 7 the first time I got alone with a girl and played with eachothers private parts. We didn't really know what was going on, but it was sure great fun. I've had a very unsheltered life, and I may have seen some things as a kid that I shouldn't have seen. But I am stronger today for it, and I wouldn't have wanted to grow up any other way.