When ypu are salaried, they will give you that much tasks that you can only do it in 80 hours. So no, a combination of salaried and hours is what is needed for the people working.
As a European, this is how it works. Having gliding hours to work is possible within that. I know people who work 4 days instead of 5 days and still do the needed hours. I know people who have very lenient working hours and can start anywhere between 7 and 8. Also working longer and shorter weeks.
Much depends on company to company. Where I work and the fuction I have, there is no way I could do that, It depends on the job, the company, the manager AND the employee. If I have a hard working staff member, I am more lenient than with a slacker.
I have send people home earlier because there was nothing to do, but believe you me, that was due to external issues (No network due to reasons). It was never because there was no work. If that happens once, people can go home. If it happens many times, you either have to many people working for you and you need to fire some, or you have other issues, that can be solved in different matters that you are insured for as a company.
In Belgium we used to have a difference between blue and white collar workers and that has been solved. Peole are now workers with the same rights.
You are paid for X hours per month, so you do what they tell you to do for that amount of time. Note that this is per month, not per week. And it depends on the situation.