The New-PfaRestOperation to query for tags only matches against the vvolUUID, but it should also match the tag name.
Other tags, like VMW_VVolParentUUID can have the same vvolUUID and will match here when they should not
What is:
"?tags=true&filter=value='$($vvolUUID)'"
Should be
"?tags=true&filter=key='PURE_VVOL_ID' and value='$($vvolUUID)'"