I don't believe to be true. If I recall correctly at the time of Dubas firing, Shanahan had already commented publicly that the core 4 were coming back for 1 last chance.
By the time BT arrived, he inherited a situation from above with a mandate that "We can and We will" is all coming back, and so Treliving's hands essential tied in regards to core 4.
That changed after this year with a new CEO and another disappointing playoff exit.
Shanahan takes blame for early exits, Core 4 changes on the table
"Our results in the playoffs have not been good enough. That's on me," Shanahan said.
Shanahan, alongside general manager Brad Treliving and Maple Leaf Sports & Entertainment CEO Keith Pelley, met with reporters one day after the team fired head coach Sheldon Keefe following his fourth opening-round exit in five years. Shanahan said he appreciated Keefe taking the blame for the playoff letdowns in Toronto, but said the "unacceptable" results are on him. He added that all options will be on the table this off-season as the Maple Leafs look to take a step forward.
“We will look at everything this summer and will consider everything with the intention of making the Maple Leafs better and to win,” Shanahan said, declining to speak on the future of any specific players.
Shanahan has continuously backed the team's "Core 4" throughout his time in Toronto, but struck a different tone on Friday, noting the time for patience may be at an end. Captain
John Tavares and winger Mitch Marner are both entering the final seasons of their contracts after Treliving extended both Auston Matthews and William Nylander this season.
"It has certainly become evident that we have to assess all of those things and assess if we have to do some very difficult things to make the team better," Shanahan said
Shanahan takes blame for early playoff exits, all options are on the table for Toronto Maple Leafs | TSN