How is Matteau the top prospect?
Look at who wrote the article.
The teams themselves provide the top 10 rankings for THN's Future Watch issue. There can be a conflict of interest at times. The writer who did the Islanders' article a few years back noted that they purposefully left off Kevin Poulin and Casey Cizikas in certain years because they hadn't signed yet. Writer said later that the team knew internally that they were top 10 prospects, but they didn't want the deal with the PR if they went back into the draft.
Similarly, Frederik Andersen was left off Carolina's top 10 list a couple years ago for the same reason. A few Hurricanes' posters were annoyed at The Hockey News, but I had to remind them that there was a reason he was omitted. Andersen went back into the draft a few months later and was taken by Anaheim. It would have looked a little worse to the casual fan if Carolina had listed him #3 and lost him.
As for Matteau last year, the teams provide a top 10 ranking and it's crosschecked against THN's poll with the scouts. THN does its survey right after the WJC, so there is usually a huge bias towards players who participated. Matteau came in #34, Santini was #67, and Severson was #71.
As much as I'm not a fan of Chere, he's not the one making the list.