https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.resmgmt.doc/GUID-EB72D358-9C2C-4FBD...
It says on that page that snapshots and backups are not supported today. it is not really clear if that goes for the vpmemdisk, but I would expect that as it acts as a datastore that those functions work, unfortunately I don't have the ability to test it.
