If you want to get technical, it is only an option for the union. Even if they exercise it, their average share for the life of the new CBA will certainly be lower than 57%. Also, the definition of the hockey related revenue is being changed, so the players would get 57% of the lesser total, which would be a defacto decrease in salary.
Not to mention the fact, that the current system was put in place by the NHL, who used the last lockout to roll over the players union and force them to accept this CBA. If you listened to Bettman speeches then, the expiring CBA was going to set he economic house of hockey in order. And now the system they devised is suddenly favoring the players? FYI, average share of wages, salaries etc. in all the other industries of American economy is near 70%. So the owners are already getting a good deal.
What it amounts to is that the league appears to try to shake down the players at the end of each CBA period for as much as they can get away with. And lock them out if they resist. Rinse, lather, repeat every 4-5 years.
Personally, I resent their bully tactics that result in my loss of enjoyment of my favorite sport.