The smb3 encryption feature can be enabled two different ways - at the SVM level or share level. If applied at the SVM level it will require that all clients accessing SMB shares on the CIFS server be capable of negotiating encryption. This is a global setting that effectively requires its use. The second method by which it can be enabled is on a per share basis. If you have a mixed environment that contains clients who do and do not support SMB Encryption, this provides the most flexibility to using SMB encryption. This approach of both per SVM or per share is how Microsoft implemented the feature when the released SMB3.
ms blog about encryption in smb3:
https://blogs.msdn.microsoft.com/openspecification/2012/06/08/encryption-in-smb3/