McCagg sounds like a scout who loves the player for other reasons and is trying to excuse away a legitimate flaw. I'll admit I haven't spent a ton of time on the guy, but he presents to me as a pretty clear case of tunnel vision. When he gets the puck, he has one objective and it's to get the puck to the net. He seems to only consider his teammates when they're either right in front of the net (i.e. in his line of vision) or when he's run into trouble, and usually if you get to that point as a puck carrier it's too late.
He could still become an effective player given his size, speed and puck skills. If everything is directed towards the net, that isn't the worst thing. Perhaps this is too obvious a comp, but Nichushkin comes to mind as a guy who's a horse moving in one direction, but it's a good direction.
Personally, I'm just not a fan of prospects who are already showing signs that they don't see the ice well. I tend to believe you either see the ice or you don't, and if it's a problem at lower levels, it's going to be a bigger problem at NHL pace. He wouldn't be in consideration for me at 21, but I get the appeal later on.