The API method in the Knox Premium SDK, setAllowChangeDataSyncPolicy(RCPPolicy.CONTACTS, RCPPolicy.EXPORT_DATA, Boolean), set to true or false enables or disables the option to sync the contacts of the container with the personal side. You can view the function of this feature in the container through Knox Settings > Share data > Contacts (from Knox). So if you set it to false, then the Contacts (from Knox) check box is greyed out and the user cannot sync the contacts. If you set it to true, the user is able to select the Contacts (from Knox) check box, and then the contacts of the container is synced with the personal contacts. You can verify this by going to your contacts app on the personal side, and see if container contacts are listed there.
If you are looking to enable the ability to move contacts off the container to the personal side, you have to enable the API method rcpPolicy.allowMoveFilesToOwner(true). This enables the option in the container to press on a contact and move it to the personal side.