Addressing some points
First of all the process described on the Microsoft website means that the volumes with the VSS enabled must be run on a VSS enabled computer to extract the data. Shadow Analyser will allow investigators and data recovery people to use a disk image, without the need for mounting, and recover data that way. These files have essentially been reverse engineered so that we know what blocks belong to where without having to use a computer with VSS enabled. This means that it is also operating system agnostic too so you could view the contents of a shadow volume whether on OS X, Linux, XP, Vista, etc.
Second, when you securely erase files on a VSS enabled system the files are still stored on a volume shadow file so, unless you turn off the VSS service (thereby losing all system restore capabilities) any securely erased files will still be contained with the shadow file.