People fought for 40 hour work week. If everyone works more hours it will kill productivity and also just suck.
I am with you that this stuff is an effect not cause of declining worker power, but the fear this will further erode old victories is genuine and shouldn't be dismissed.
Ultimately, yesterday's worker power is not a substitute for a lack today, but (hopefully) once that is somehow fixed, it is really important to turn these norms stuff back.