The release tag client/v6.1.0 is for VolumeSnapshot APIs and client library which are in a separate go package.

API Change

• Add VolumeSnapshot v1beta1 manifests back so that existing persisted v1beta1 objects are accessible via the new v1 API, however, VolumeSnapshot v1beta1 APIs are no longer served.
  Action Item: Please update to VolumeSnapshot v1 APIs as soon as possible. (#718, @RaunakShah)