No it is not unfair to expect already great things from Matthews at men's top level. I believe that if he is really worth of being the number one pick and is as special as his fans here all the time claim that he is, he would be already able to contribute even better than he has done in this WHC tournament. Especially against teams like Hungary or Slovakia.
For sure I don't claim that he is not a great prospect. But for him to be really BPA in this draft, he should really be able to be much more impressive. Laine and even Pulju have been that great this year. Matthews is still a great prospect. He just needs much more of intensity and consistency. And he sure needs to improve his passing game and defensive play a lot to be a really great two way center. But he sure has nice offensive instincts. He is already a beast in front of the goal, and his wrister is really good.
I have to say that to me he looks completely like a winger though. Maybe it would be in fact a good move to switch him to the wing? He doesn't seem to be that great in faceoffs either to really keep him as a center. As a winger he could fulfill his obviously very high offensive talents been better.