i can't figure out what some of the commentary here is borne from. "you're not working 100% of the time so it's ok if they ask you to work outside of normal hours" is sadistic.
I took parent to be arguing that because people get paid at the office even though they aren't working 100% of the time, the same logic would dictate being paid when not at the office. The percentage flip would just mean that they aren't 100% doing leisure activities.