That's the standard practise, sure
But when your own GM comes out earlier in the offseason after landing the biggest fish in free agency, and more or less guarantees that the key cogs (Matthews, Marner, Nylander) will remain intact and signed, perhaps it sends the wrong message to suddenly get frustrated and jettison one of them into the sun the way Shanahan just did.
I don't think he jettison'd him at all. He also said they love Willy, think he's a great player, and want him to be apart of this team for the long haul.
However I think this was a clear message, not even to William himself, but to Michael Nylander and Lewis Gross that they aren't going to jeopordize their plan and structure they have to overpay a player.