It does usually 'make sense' so we can agree on that.
There are usually 2 players on a line that seem to get a lot of love for 2 way play. The winner will always have that guy a little bit down the ballot. So Marchand with Bergeron, Reinhart with Barkov, and even to a lesser extent we have Matthews with Marner.
Now what is interesting about the Matthews/Marner thing is that the media can't seem to get on the same page, due to the fact that they don't play traditional positions. Marner is the facilitator and the one you want with the puck on the stick most of the time. Since Matthews isn't driving the play on his line, with or without Marner, he should be one of the first guys back and have the freshest legs to pressure defenders looking for a takeaway. There are tons of guys who do that better than him, like Jarnkrok who wouldn't be in the league if he didn't hustle on the penalty kill. But there are few guys who can be trusted with the puck on their stick going up ice, and that is why Marner will always get a lot of penalty kill minutes, much more than Matthews, and likely always steal Selke votes.