MAC OSX group policies are not applying
Even though both Once and Often shouldn't be configured for a user or machine policy at the same time, it's possible to do so and causes issues with policies not applying. To confirm if this is the issue, reset the configuration of both user and computer manifests, apply the settings through vgptool apply and by logging into the computer, then set it the way you want to set it and reapply (while also logging out then back in).
After doing that, it should work properly, however, while both of those were configured at the same time, neither were being applied.
Do not apply once and often at the same time to the same policy.
To reset the settings, do the following:
1. Navigate to the preference manifest in the Group Policy Management Editor.
2. Right click on the "Screen Saver ByHost" manifest.
3. Click on "Reset Configuration".
4. Run `vgptool apply'.
5. Run `vgptool rsop' and ensure that the setting no longer takes effect. Repeat steps 4-5 until it is gone from the rsop.
6. Logoff as the user.
7. Login as the user. This will reset the user's settings.
8. Define the setting as either Once or Often (NOT both).
9. Run `vgptool apply'
10. Run `vgptool rsop' and look for the setting. Rerun 9-10 until it shows up.
11. Logoff as the user.
12. Login as the user.
13. The new setting should take effect.