If this trade were made on Friday afternoon, I would feel differently about it. At that point you truly are down to "light return" or "no return", and I can understand sucking it up and accepting the light return for the reasons you mention (the Dorion handcuffs and goodwill benefits). But 48 hours out from the deadline, there is still a third potential outcome, which is that Florida comes back with a better offer. They might be saying this is last and final, but for Tarasenko at 50% retained, Staois doesn't have to believe them.
By settling for this trade today he banks goodwill with the players, which is absolutely a positive. But he also loses the flexibility of that retention slot (which can be used to get a mid round pick), and he signals to rest of the league that he is a negotiator who'll cave on price rather than walk away if he doesn't get what he considers acceptable.