Raevyn Rogers: 3secs improvement since she was 19yrs of age. BTW, I checked the last Olympic 800m. Every athlete - apart from Mu - improved the time they did at 19 by anything from 3sec to 9sec!
And some great 800m runners never improved past 19 - like Ryun and Amos. It seems hard for you to grasp that no two human bodies are the same.
Amos was a doper.
Ryan was more of a miler in ancient times.
Peaking at age 19 is really strange in athletics I think, barring injuries.