Named Version are the milestones of any infrastructure design project. 

Ideally named versions are meant to be created when certain milestone of the project is reached and those are needs be reviewed from stake holders. Those Named Versions can be based on stage of project completion or it can be time bound to check the progression of the project. 

Named Versions can be created from iTwin Synchronizer itself while, syncing any changes to iModel. It is up to the project team member to decide up on weather their latest changes are qualifying for certain milestone and same need to be reviewed through Design Review.