Yeah that's the thing with junior sports. No matter how good somebody is until they actually do it at a senior level their just 'potential' or talent. Sometimes you see the talent play out (Lebron James, Usain Bolt), sometimes you don't (Ronnie Fields, Mark-Lewis Francis).
Personally I know 1 guy that's 20 and runs 100m in 10.91 and 200m in low 22s. That's pretty fast but 6 years ago when he was 14 he was running 100m in 11.53 and 200m in 23.17. In his case he was just an early developer and so despite training for the past 6 years he hasn't managed to even improve a single second on either of his 100 or 200 times. But back when he was 14 everybody was on his nuts because his times were impressive for his age.