The SegmentWriter and its related classes accept a SegmentVersion argument. This is confusing since that version is only stored in the segment's segment version field. The writer cannot and does not actually write segments at older version than the latest (12).
I suggest we remove the explicit segment version from all classes where it can be specified and hard code the segment version to 12 for now. This is the only segment version segment-tar currently supports anyway. Should the need to support other segment version arise in the future, we need to decide at that point how to parametrise segment-tar on the segment version.