At least up until version 4.2 (I cannot say regarding versions 5.x, since the documentation is missing completely: Missing documentation for all Stardog 5 versions) versioning was properly documented.
Looking for "Versioning" in the current version only points to the missing feature in Stardog 7 beta, but nothing is said regarding Stardog 6.1.0
The feature is supported in 6. and we will bring back the versioning section to the documentation. Versioning is not supported in the 7.0.0-beta version and this feature will most likely appear in a different way in 7.* releases but these changes will not affect how the feature works in 6.* releases.