The reason that policies can be very powerful in managing your business environment is that you can create a single policy and, with just a click of the mouse, have that policy applied to hundreds and thousands of devices. After they are assigned, those devices automatically apply that policy. You can be confident that the policy is sent and enforced on the device.
Now if you decide to change a policy, simply edit it in ZENworks Control Center and the system automatically updates all assigned devices with that updated policy. You don't need to do a thing.