TBH that was the least of their bad decisions.
Cristall was noticeably bad at the U18s 1.5 years ago despite similarly torching the WHL. He's an engine who needs the offense built around him.
Unfortunately, he exists in the same era where Gavin McKenna is simply a better engine, and Cristall has never shown any type of fallback game. He's not the type to successfully adapt to a short tournament in a different role and the WJC is not necessarily a showcase of future NHL successes, so I don't mean that as an insult of his future prospects.
All that to say, there are plenty of other omissions to this Team Canada's forward group who would have had a greater impact in a secondary role (Sennecke, Misa, Wood, Iginla).