Big body, pushing through defence, great shot, great skating, yet limited playmaking. Those are the qualities that usually attribute to a 3rd liner. There is no reason you can't play top lines and pp with those skills though. It all will depend on how his skills translate to pro hockey.
I see a lot of young Nichushkin in Vilmanis, and, ironically, Nichushkin is the one who shows that depending on different factors, you can be either a borderline star, or a meme player known for not being able to score.
People are cautious because for a 5th rounder, even making it to the NHL as a third liner is a big success. Plus, he is 20 years old, and you would expect this kind of dominating performance should a player have any remote chances of making the NHL. His true potential will be seen next year in th AHL. Currently, I am cautiously optimistic.