Quoting: HockeyScotty
Perhaps it had something to do with the arbitration filing by the Flames? There are probably some CBA experts on here that can comment better.
CapFriendly listed themselves as the "source" for the signing information so not sure if there is a 3rd party confirmation.
The reason Calgary signed Tkachuk was to enable Florida and Tkachuk to get the 8th year. If the contract was signed after Tkachuk became Florida's property, the max Florida could sign Tkachuk to would be 7 years. They would have to wait until after the trade deadline to be eligible to sign Tkachuk to an 8 year deal. That would present an immense risk for both sides since they would have to sign a 1 year deal, and then a 7 year extension January 1st. Or, they could sign a 1 year deal, and an 8 year deal after the trade deadline, for 9 years total. Either way, it presents an immense risk because with a 1 year deal, there would be nothing binding either Florida or Tkachuk to a long term extension, and either side could change their mind.
There is obviously the risk that Calgary could back out from the deal after Tkachuk signs for the sign and trade, but something like that would be a career killer for a GM. No player or agent would trust the GM or the organization ever again, which would make conducting business very difficult.
In short, Tkachuk technically signed an 8 year extension with Calgary last night, and was immediately flipped to Florida after the extension was signed. But for all intents and purposes, Florida likely negotiated the actual extension since they were the one who would keep the extended player.