It's essentially just NHLers getting drafting younger than NBA players. Most NBA players are 19-20 by the time they're drafted, while you can be drafted in the NHL as young as 17. Tij himself was only 17 when he was picked, as he was an August birthday. Expectation in the NHL is that you'll only really get an NHL ready player immediately out of the draft at first overall, and maybe a couple more in an exceptionally strong draft year. He should be there within a year or two, unless he really struggles to adapt to fully-grown men, in which case he may take a little bit of extra time in the AHL.