this is created when you run a benchmark with 'proxmox-backup-client benchmark' on a datastore.. It's probably unexpected to leave that group around, so you could open a bugreport for that (though it might not be possible to remove it if the token/user used does not have the right permissions to remove a snapshot)
recently the content view changed to also show empty groups (previously only groups with snapshots were shown, so that's maybe the reason it has changed for you)