You need the whole running PBS to be able to restore any backups. There are no individual backup archives like when using VZDump that could be restored by PVE without a PBS.
And PBS needs the whole datastore folder, so your "/mnt/datastore/backup-MTL", with all files and folders in it (also the hidden ones like "/mnt/datastore/backup-MTL/.chunks") to restore any single backup snapshot. That is one of the reasons, next to stuff like ransomware protection, why you shouldn't run PBS on the same server you guests are runnung that you want to backup to your PBS. If you lose oyur PBS + datastore, you won't be able to restore any backups. If you lose the PBS but not its datastore, you could install and set up a new PBS but only after that you will be able to do any restores.