I don't think the 8-hour work day was accepted during the industrial revolution because job providers were convinced of productivity gains. It was won due to the leverage the labor unions and workers had over job providers.
The whole thing rests on whether workers can maintain their leverage in the AI era. That leverage is being eroded by the attempt by job providers to decouple humans from production and productivity (whether they will be succesful in this iteration is, as you say, debatable). The other axis is the attempt to erode democratic norms in order to prevent the majority from checking the power of a wealthy minority.
Once those two points of leverage are completely eroded, the only leverage left is mob power. And as history has shown on multiple occasions, excercising that leverage is ugly and messy.