Well, where did Miguel Tejada and Bartolo Colon 'hide' from the time they were actually 16 to the time they signed? Just because scouts thought they were 16 when they signed doesn't matter. They were actually 18, 19, 20 when they began and made it big. With the crackdown, many of these kids couldve been claiming to be 16 a year ago, and now come out at 18 or 19.
Physical development has a lot to do with it. Personally, the summer after my junior year I went from 83-84 to 88-89. A year later,I was 91-92. That's 8mph in 2 years.
I don't pretend to know how everything works out there. But I find it hard to believe every kid out there is either a prospect by 16 or written off forever.