As a teenager, I have to agree with most of this. Playing a character of that age means I can draw directly from my own experiences and emotions when considering how they would react to situations (accounting for personality differences, of course) instead of also having to consider how age and experience would affect an older character's decisions and thoughts. I don't want a thirty year old man having the mindset and inner monologue of a teenage girl, for instance.

My oldest character was probably around 44. My youngest was 11. Quite a few of my story protagonists are teenage girls, though, and they tended to age up as I did.

Also, IMO it's slightly easier to get characters in that age range to do something interesting, on the grounds that it was a spur-of-the-moment decision/they didn't know it would result in things happening/they were driven by their emotions.