According to this report it would seem that NHLPA isn't exactly onboard with the NHL's decision to move games to the this facility. With the facility only being able to seat 3,500-5,000 the NHLPA has concerns about how this will impact Hockey Related Revenue.
HRR is represented by any form of revenue generated by that team related to hockey games (Concessions, Ticket Sales, Etc.) This number goes on to impact things like the salary cap and players percentages, so it's understandable that players have an issue with the NHL willingly accepting a stadium this small.
This situation continues to change and cause issues for the NHL and the Coyotes organization.