What I found in my testing seems to mirror what that article says. It all seems to be about the calling license. If you remove the calling license from users you can bulk them with a CSV file. Problem is, dropping their calling license removes all their calling settings (voice mail, hot design, etc.) and if they have a device assigned it deletes the device from the tenant.
If you move them one at a time in Control Hub and go through the wizard, it retains everything and moves them to the new location.
This is a pain as the "manual migration" process for porting numbers to Cisco Calling plan involves creating a new location and moving users (https://help.webex.com/en-us/article/nousk9ab/Get-Started-with-the-Cisco-Calling-Plans#wbxch_r_pstn_migration_paths_wxc).
