Once bitten, twice shy.
If I'm Brad Treliving, I don't sit by the phone with fading hopes that William Nylander will sign a new contract before reaching free agency. Lewis Gross screwed him over royally on the Johnny Gadreau contract negotiations, and I don't think Treliving would have much of an appetite for a second serving.
Of course, it's not all on the agent. However, Gross is Michael Nylander's business partner. Nylander is a player agent in Gross' agency, Sports Professional Management [SPM].
Michael Nylander himself was never an easy or reputable player to deal with on a business level. The Edmonton Oilers complained bitterly when he reneged on a promise to complete a deal, leaving them high and dry when it was time to sign other players instead:
https://www.cbc.ca/sports/hockey/oilers-cry-foul-over-nylander-signing-1.662061
Michael Nylander and Lewis Gross were both involved with William Nylander's contract hold-out to the very last minute of the deadline to sign his current deal, and that can't engender much trust either.
Gross is also Rasmus Sandin's agent, and I don't imagine the the Leafs shed a tear over not having to deal with either of them on Sandin's next contrat.
If I'm the Leafs, I want to know if Nylander will sign a new contract soon, which would be Plan "A"; and if not, then to trade him for whatever they can get, which would be a very poor Plan "B". Plan "C" -- getting burned again in free-agency -- would be pretty much unthinkable, even though Nylander's unsigned trade value would be low because the next team will have the very same problems in reaching a contract.
William Nylander is a very good player, but dealing with his contract is a pain in the ass.