To be honest, I've always actually wondered how little the hockey world seems to understand about human biology. Some prospects are fully grown men with a beard at 16, whereas others are physically kids until they hit 20. If someone dominates the juniors because his physical age is 2-4 years ahead of the others (and not only the height), there's a chance that he will not be a major contributor when the others catch up. Of course he will be hyped, he will get more chances than most others, but in the end he might be seen as "bust", even when he did reach his full potential.
Personally I don't see being an over-ager any flaw at all. In this case it's just one year, and how many 2019 picks have already played in the show? So far 5. If Chinakhov makes it next season, he's still way ahead of most 2019 picks, not to mention 2020.
And all the dissing around him, just because he reached full height only at 19. Which is perfectly normal for a healthy young man.