A good counter example would be Mikko Rantanen actually. Before his draft season, his skating was terrible by all accounts. You can see during his draft season, though, that it improved markedly. However, Mikko is almost a year older than Jesperi.
Players get better at everything naturally as they get older, so, Jesperi will be a faster player in a year's time. What we're talking about is moving between quantiles within an age cohort, which will naturally be more difficult, and thus you'll find fewer examples of it. But in the end, these are just skills and humans can learn them until a fairly advanced age. Way past the age of 17 anyways. If that weren't true, drafting would be shooting fish in a barrel.