I don't think it's so much Nylander himself holding it up, I really think he wants to get this thing behind him and play with his friends.
He's under a ton of pressure from both his agent and his father to sit this out and "get his worth" (AKA pay way more for my hypothetical potential).
His agent is obviously aware of the leverage. If Nylander sits out it messes with the best roster the Leafs have iced in 50 years, he knows this and he's utilizing it. Now the decision is ultimately Willy's to make, but this is probably where he's being pressured by his dad to listen to his agent and sit out so he can get paid. Michael Nylander was not a loyal guy at all, he jumped ship every 2 years to another team and made it past the 1st round once in his entire career, and only played 47 playoff games his whole career. He obviously prioritized money over team loyalty, success and legacy. Now is he trying to impose this same ideology on his son?