In junior, it's not nearly as rare or as special as in the NHL. Not that it's not a nice achievement, just that it's a lot more common in juniors than you'll find at the NHL level.
In terms of achievement relative to rarity, 40 goal scorers in junior would probably equate to how impressive it is to hit 30 goals at the NHL level.
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As to Dal Colle and the lack of discussion, I think it's because he's not a flashy player. HF, in general, seems to fall in love with prospects who rack up Youtube video highlights and play a flash-and-dash type of game. Dal Colle simply produces, but likely won't make many highlight clips doing so.
He's one of the best prospects out there. He's simply not flashy enough to satisfy HF's fancy, IMO.