To be honest I'm not sure, I saw the same on one of our vCenter appliances that is the backup / failover shows the same for the OS field.
Scanning Tip
I found vCenter scanning worked best for our environment by creating an asset type scan of VMware vCenter server that runs every 4 hours. That allowed us to keep the ESXi Server assets up to date as they would fail an SSH scan if you follow best practices with disabling SSH on ESXi hosts.