That's typically not how contract negotiation work in these cases. Team/player presents their best case among the suite of recent comparables. Matthews is not a comparable for Marner.Marner *did* get $10.9 million when Matthews got $11.6 million on their last deals, so I could see Marner's camp arguing for within ~$1 million of whatever Matthews ends up getting. There's precedent for it.
Your view also ignores player performance since they signed their last contracts. If Marner did much worse, or Matthews was far better, it wouldn't justify Marner's camp just going "oh well I always earn $1M less than Matthews and that's just how it is".