NHL players get 50% of hockey related revenue. If the contract values across the league total less than 50% of HRR, then a correction would be applied to give them more than what their contracts state. If contract values across the league total more than 50% of HRR, then escrow takes some $$ away.
The precedents set by star players going for big money or taking discounts can influence distribution of that money between top end vs lower end players, but otherwise it doesn't impact the total amount of $$ going to the players.
So I don't see why the NHLPA should care. It's arguably a conflict of interest if they do, because if they push for the MacKinnon's of the world to go for bigger contracts, it means less $$ available for the depth guys.