I don't know if that's necessarily wrong of them. There isn't any precedent for hourly workers to be paid when they're not working. The "four day workweek" as described simply means that any time over 32 hours a week is overtime. Hourly workers in general don't really have a "workweek" anyway because they will often have multiple jobs or will work whatever shift they can pick up that works with their schedule.

They understood how the 4-day workweek works based on how the 5-day workweek works. I think maybe you need to listen more to them and try to understand your own proposition better.

When companies voluntarily implement 4-day workweeks, they are literally either cutting 8 hours or doing 10-hour shifts. They do not pay for hours not worked.