Retrospect for A/UX: Backing Up Shared Data

I selected the Shared Data folder as a subvolume in my scripts expecting that Retrospect would backup the data on the external hard drives attached to the Workgroup Server 95 (there are mount points inside that folder). Why can't I just select "Shared Data" and have it backup all the mounted volumes?
The "Retrospect A/UX" manual states in two places that mounts points must be specifically scripted to back up individually.

On Chapter 1 Page 11, the first paragraph mentions "you need to specify each mount point as a subvolume and back it up as a separate source"

On Chapter 2 page 14, there is a "Caution at the bottom of the page that reads "CAUTION: If you fail to specify mount points as separate source subvolumes, any data stored on additional hard disks will not be backed up.
Published Date: Feb 19, 2012