Let me start by saying I agree with you: Smith is a tier below Fantilli and Carlsson and we all knew it at the draft. It's why so many folks wanted to take the swing on Michkov.
That said, I'm posting to share Grier's POV on this, at least the one he publicly shared yesterday. Some fan asked why Smith wasn't in the NHL like Marleau was at 18 and his answer started with "Will is as good as Leo or Fantilli." Then went on to say that Marleau was a freak who looked 27 at 18, and that Leo and Fantilli are both fully grown men while Smith still looks like an 18 year old kid. That they're going to be patient with prospects to make sure they're ready for the rigors of 82 games vs. men.
I like that take, other than the fact that I probably disagree (and who knows if Grier even believes it) that Will is in the same tier as Leo or Fantilli. We will see over time (no shit). But it makes sense not to rush kids to the league if they're not fully grown yet.