I think we can agree that if Matthews played 60 minutes a game, his /60 stats would go WAY down due to him being dead tired for most of the game. On the other extreme, if he played just 1 minute a game his /60 stats would go down because he'd never be warmed up and loose. So, indisputably, the amount of ice time a player gets a game will affect their /60 stats.
The question then becomes, what is the precise sweet spot? It's fair to suggest that someone playing 17 minutes a game would be able to put more hustle in every shift than someone playing 23 minutes a game.
So that's what the argument has been.
Matthews has simply elevated his game this year That's it. Kudos to him. In past years (whether it was battling through injuries, motivational problems, not liking the coach, etc.), Matthews would often take shifts off. Sometimes even games.
That hasn't happened this season. He's a beast each and every shift. I sincerely hope he keeps it up.
I will agree with you that, on a small 18 game sample size so far this year, he's been McDavid tier.