Are you that dense that you don't understand that people mature differently? My best friend to this day had armpit hair at 11 in elementary school. I went from basically peach fuzz to body hair everywhere and a full beard that grows in nearly a week from 17 to 18.No, it isn't flawed at all. Searching google about refugees lying about their age gives me this guy:
Sitting there going, "uhh yeah just lemme look at the guy, I can totally tell!" is an utter joke. You'd be laughed out of any scientific forum or court.