I'd basically agree, though he's been playing equal minutes to Soucy recently, and has averaged not far off through the season. It basically comes down to whether you believe he's a second-pair guy, and should be paid like one, or if he's a fixture on the bottom pair left side, and shouldn't be paid more than that.
With Hughes-Soucy down the left, you aren't really in a pinch, and shouldn't be in a rush to give Zadorov second-pair money he wants to anchor the bottom pair. Given he's pretty close in age to Soucy, you'd really have to think Zadorov is your long-term second-pair left-side guy to justify signing him.
I'd think from a roster perspective, it would make more sense to let Zadorov walk and spend that money on a right-side defenseman.