Why not? According to most of the "experts" on MLB radio, Berrios wants to test free agency. If that happens, the Twins have nothing to show for keeping him. If they trade him now when he will be the #1 pitcher in demand at the trade deadline (again according to MLB radio), they get something back. And they can still try to sign him when he does go to free agency. Win-Win.
People seem to forget that a contract involves two sides. If one side doesn't want to sign (Berrios and probably Buxton), then there will be no contract no matter what the offer is. This isn't baseball that existed before Lou Brock.