Seafile Server 5.1 Upgrade - Sublibraries Dropped But Shared Subfolders Still Work

Any of you that bother to read thechangelog for the Seafile Linux Server before upgrading might have seen that 5.1 states:

Warning:

• The concept of sub-library is removed in version 5.1. If you need to sync an sub-folder of a library, you can create a group and share this folder to the group.
• The group message reply function is removed, and the old reply messages will not be shown with the new UI

I had thought that this meant all shares of sub-folders within my libraries would no longer work and I would now have to share at the library level instead now. Well after the upgrade everything is working exactly as before so I am now confused as to what a sub library is. At least you now know and may feel safer about upgrading.