Hockey Canada has a ridiculous internal policy in which they "graduate" players from a level if they have played for Canada at a higher level. Since Misa played at the Hlinka (U-18), Hockey Canada won't name him to a lower level, such as the U-17, even though he is still eligible. Bedard played at a second U-18 after the cancelled U-20, but that was a unique situation.
Typically, you will only see exceptional status players play at the U-17 for Canada in their 15-year old season (Ekblad was an exception). I can't think of another nation that does this. It seems to me like its one of those "we've always done it this way" type of policies, similar to sending 3-5 teams to the U-17 the last decade when some of them were clearly outmatched and getting blown out 11-1 in a gold medal game.
