To me, if you are not free to walk out the door and do whatever you please, you have an obligation to an employer, and are therefore working. I worked a college job fixing bowling equipment and they tried to make me clock out for my meals. I refused unless I was then free to leave the building. As if I have to be there on call then I am still working.

Amazon is not allowing these people to walk out the door and go home. That is taking their time for company policies. So that is working.