No.
Marner is a winger, and we've seen repeatedly that centers carry a price premium to wingers. Only elite centers have garnered the truly upper echelon AAVs (McDavid, Mackinnon).
Marner does not have production exceeding that of other big, superstar winger contracts - Pastrnak did not sign for ~$13+M.
Regarding walking to UFA, sure, any player who can reach UFA status has that option. It doesn't change the set of relevant comparables.
Nothing you've said has any bearing on my response. What Marner is worth and what he'll get are two completely different scenarios. All of which will be impacted by Matthews' contract. Like I said, if Matthew gets 13.5-14M, Marner is immediately demanding 13M or he's just not signing. You're never getting him at Pastrnak's salary.
Treliving has absolutely zero leverage going into negotiations. Marner has a full NMC and will be a UFA. If the Leafs sit firm on 11.250M, Marner can either pick his trade location (which kills his value) or, ironically, do exactly what Tavares did.
If the Leafs ink Matthews to his big payday, they may as well toss an almost identical contract Marner's way because he's not taking much less. Toronto's chance to make a splash was before July 1st. Now they're stuck paying Matthews and Marner whatever they want or they're losing them for nowhere close to their trade value.