1. Honestly, yes. Hockey is very random. Goalies even more so. Matthews can't make Kallgren stop the neutral zone face-off circle shot from Gudas from going in. But that counts as a GA against for Matthews. If you want to judge skater defense, look at the defensive metrics players can more directly control:It's "comically bad" to judge a player defense by the amount of goals that happen while they are on the ice?
Being "One of the best Leafs forwards" at something is not an accomplishment that makes someone eligible for the Hart, sorry. But on that note, if he isn't the best, are you implying that the Leafs shutdown line coaches their goalies to be better when THEY are on the ice? You can't have it both ways.
And it still won't have been done in decades since the definition has always been from the start of the season. It's like this malarky of him having the most goals by an American "born" player- Brett Hull, who was considered American because he grew up in the U.S. and represented them internationally, is the actual record-holder for his country and Matthews likely never touches his totals unless there is a significant rule change in the next ten years. However, there has to be this narrative twisting and turning to make it seem like a bigger feat than it is. That's Toronto sports media for you in a nutshell.
Per Natural Stattrick (min 200 5v5 minutes)
Matthews:
-2.57 scoring chances against per 60 relative to teammates (3rd best among Leaf forwards)
-0.81 high-danger chances against per 60 relative to teammates(3rd best among Leaf forwards)
-0.35 expected goal against per 60 relative to teammates (1st among Leaf forwards)
He reduces the number of scoring chances, high-danger chances, and total expected goals against his team when he's on the ice.
2. No. But the combination of offensive generation, goal-scoring ability beyond any other player this season, and above-average defensive play, is what makes him a Hart Trophy candidate.
Your comment about goaltending "coaching" makes absolutely no sense. I'm not arguing from the place of looking at raw goals against. The Leafs' high-end shutdown players (Kampf, Mikheyev, Engvall) are strong defensively because they prevent scoring chances against. Not because Mrazek/Campbell/Kallgren happened to stop the stoppable shots while they were on the ice. This is exactly the same logic I used to support Matthews being a strong defensive player. This just demonstrates that you're not really going to grasp these concepts.
3. What is the definition of "50 goals in 50 games"? It's....exactly what it says it is. It would be an impressive feat, regardless of whether it happened from the start of the season, or in the middle. I'm not from Toronto. I'm not a Leafs fan. I'm just unbiased and can look at the facts, look at the feats, and objectively say these are very impressive and certainly worthy of major Hart consideration, if not winning the trophy outright.