The NLPA and NHL have decided to give UFA's all the power in exchange for RFA's and ELC contracts with next to zero rights. The NHLPA won't get better rights for ELC's or RFA's in the next CBA unless they give up UFA rights. It is a balancing act.
Guys like Trouba have no choice but to play hard ball, sit out, and force a move, if they are unhappy with what is being offered or their playing situation. With Buf ahead of him, and maybe not wanting to play the left side, I can see why Trouba is better off long term trying to force his way out now. If he went to Phoenix, they could sign him to a deal that would take him to his UFA years. In the mean time, he is a 1RHD playing with OEL. That is way more attractive than being behind Buf, playing for less money, and on his off hand. All of that could hurt his market value when he is a UFA. Chevy still holds the cards and can let him sit. But does he really want a guy who doesn't want to be there? This is why guys like Turris/RyJo/Trouba get traded at the end of the day.
I have no idea what is really happening with negotiations, just speculating given his situation and his agents tactics with past clients.