You can't compare the dynamic of trading a UFA to trading a player with term.
Even Stone getting an extension doesn't make it the same thing, because there is still the dynamic there where if the team doesn't pull the trigger on the best offer, they are going to lose the player to free agency.
If Nylander was a UFA, a 1st/2nd/Demelo would probably be on par with what he'd get. Maybe a bit high. He's not a UFA. He's signed for five more seasons, and in the proposed scenario the Leafs further inflate his value by paying his July 1st bonus. It just doesn't make a lot of sense.
NHL Rumors: McKenzie Updates On William Nylander And Potential Teams Interested - MyNHLTradeRumors.com
“It gets complicated, and here’s why. We said all along that a team like the Carolina Hurricanes were interested, and they are – but for the right price. So our sense of it is that Brett Pesce would be available to the Toronto Maple Leafs, but Jaccob Slavin wouldn’t be. And I do expect that the Carolina Hurricanes and the Toronto Maple Leafs will continue to have dialogue over the course of the week.”
You're making it sound absurd, but it's not like I am floating this idea of Pesce for Nylander out of thin air. It was a prevailing story when Nylander was holding out. There is a quote from Bob McKenzie above on the situation.
I get that things have changed in the last few months. The Hurricanes are on a deep run. The Hurricanes also were able to add some offense without dealing one of their defenders. Nylander also had a down season. With Nylander, I think teams who liked him won't let a down season after holding out and missing training camp hurt their evaluation of him that was based on a much greater sample size.