My only comment to the "historic season by player aged x years in the KHL" has been if young players are habitually underused in the KHL its not much of a barometer of anything. Perhaps Kaprizov was misused to a greater or lesser degree than Michkov was. Hard to tell without breaking it down by ice time, linemates, zone starts etc and even then thats not painting the whole picture.You should ask Habs fans why doesn't Demidov play as much as he deserves. It will answer your question about Michkov as well...
And that is of course ignoring that different players develop at different rates through their 20s.
This isn't even a comment on Michkov either. I'd say the same thing if Demidov posted "historic" numbers as a teen.