Graham, thank you for your reply.
You are correct; we see this problem when consolidation is needed but no snapshots are actually present. This happens occasionally after nightly backups (CommVault). Right now; the only report method we have is a storage administrator notifying us (server administrators) that a nightly backup failed; a report is generated by the backup software and then we investigate vCenter to remediate each individual server.
I will try your recommendation, Virtual Machine Metric: "Waste % > 0", the next time we have a machine that requires the consolidation. There aren't any currently in our environment.