Matthews got 14.02% of an 83 mill cap. He probably wanted 16% on an 8 year deal (aka 13.25 mill). Why people think Dubas got bent over on that is beyond me... Really, considering he got half the PP time as most of his comparables and is not really putting up much less in terms of production (especially goal production) and was receiving less ice time and support than many of his comparables, that may even end up being a steal.
Dubas probably wants to give Marner the Kane RFA contract. He was 11.09% of the cap back then, which would be about 9.2 mill on a 5 year deal now. Marner was 93 on London, so perhaps Dubas gives him 9.3 mill x 5 years, which is 11.20% of the cap. That eclispes the ceiling out of wingers who are on 5 year deals. If he wanted the 8 years, then he probably gets 2% more, which puts him just under 11 mill. I think that is also fair, considering he is an elite winger. Maybe Dubas is saying he wants to cap it off at Kane's 10.5*8 rather than just under 11*8, but we are talking about like a <500k difference. They'll probably work that out at a number both sides would like on an 8 year deal. I think that's the type of stuff you are seeing the Leafs and Marner working out right now.
The rest of it just seems like wishful thinking from other fan bases who sadistically want to see the Leafs get screwed, probably like they thought with the Matthews and Nylander contracts... Marner does not have any leverage to get Matthews' contract, just like every other elite winger before him did not lay claim to that kind of money. Marner is elite, but he's not generational. He's not better than McDavid, which is essentially what Marner would be claiming with that kind of demand, and I do not think other teams would even offersheet him at that amount. Otherwise all of those other RFA's (Rantanen, Point and Aho) are not going for less than 11 mill on a 5 year contract themselves. There is a good chance Rantanen and Aho are going to want more money than Marner, so what are they going to make? 12 mill on a 5 year deal? More than Matthews? That's pretty much where things would be heading.
I personally don't think Marner wants to go the offersheet route anymore than the Leafs do. For one, if a team does not want to match his ridiculous demands, then that takes away any leverage he had over the Leafs (by threatening to go to the offersheet route)... And then if he does get what he wants, he's going to have to be willing to accept it and risk the Leafs not matching it? Is getting paid maybe 5 mill more on the life of his contract worth more to him than what the Leafs would give him (a lot of which could not be replicated by any other team in the NHL)? The offersheet threat only works if you are willing to follow through on it, and if you think the Leafs are suckers enough to fall for it. Sorry, I don't think Dubas is that much of a sucker.