How can I mount vss snapshots and why we have to do that to take backup in window server backup?

"Windows Server Backup cannot guarantee Volume Shadow Copy (VSS) snapshots are retained. In certain situations, after restoring to a new volume, the VSS snapshots may no longer be recognized and appear inaccessible. To guarantee protection of a VSS snapshot, mount the VSS snapshot, and run a backup job on that snapshot." It's written in the doc " https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/jj614621(v=ws.11) what's this pharagraph suggesting can someone please explain it to me? I tried to find online but found very little information. My questions : 1) why we have to protect vss snapshot, does not window server backup feature takes care of it ? If no then how can I do it?