$SnapInfoSnapshot - Specifies the SnapInfo Snapshot copy name created on the
storage system. SnapManager for Hyper-V makes a Snapshot copy of the SnapInfo
LUN at the end of the dataset backup.
<note>The $SnapInfoSnapshot variable is
supported for dedicated virtual machines only. </note>
Is this VM clustered?, then it's expected behavior, SMHV currently expand this variable only for dedicated nodes.