There must be a balance. You can't just say, as you do, that employees might as well go home since they aren't working.
Why not?
As long as you are satisfied with the productivity of that employee, what does it really matter if they produce their output in 10 hours or 40?
I get that the idea is that "if they can do this in 10 hours, then in 40 hours they should produce 4x as much!" But that's clearly not reality. All that happens is that once a worker's capacity is tapped out, they find workplace-acceptable ways to sandbag
Employers can seethe about it all they want but that's the reality
I have different expectations depending on whether you worked 10 or 40 hours. The _reality_ is that you and your employer need to come to an agreement on expectations.
If I can meet your 40 hours expectations in 10 hours, then what?
You adjust your expectations upwards
You want my maximum efficiency for what you think you're paying me for, which is 40 hours
But if I know I'm going to do 40 hours minimum either way, what is my incentive to work harder and get more done?
"That's your job, it's what I pay you for, it is your contract" you say.
But you pay me either way and as long as you're happy with my output then it doesn't matter if I actually worked 10 hours or 80