How to really exclude Time Machine Backups from Spotlight-indexing? I try to exclude my TimeMachine-backup-storage from being indexed by spotlight and got some weird behaviour. The backup storage is a Time Capsule.
To exclude it, i did the following in terminal:
sudo mdutil -i off /Volumes/Time\ Machine\ Backups

Output was:
/Volumes/Time Machine Backups: 
2016-04-25 11:05:25.036 mdutil[2896:441987] mdutil disabling Spotlight: /Volumes/Time Machine Backups -&gt; kMDConfigSearchLevelFSSearchOnly   
     Indexing and searching disabled.


Seems pretty fine. But when switching spotlight-indexing from on to off, the following lines will be printed out indicating, that the Time Machine subfolder for my machine will still be enabled for being indexed:

(The spoton-command is an alias for &quot;sudo mdutil -a -i on&quot;)
However, i tried to exclude also explicitly the subfolder &quot;Backups.backupdb&quot;:
sudo mdutil -i off /Volumes/Time\ Machine\ Backups/Backups.backupdb

The weird output is:
$ sudo mdutil -i off /Volumes/Time\ Machine\ Backups/Backups.backupdb
/Volumes/Time Machine Backups/Backups.backupdb:
2016-04-25 11:05:28.815 mdutil[2914:442054] mdutil disabling Spotlight: /Volumes/Time Machine Backups/Backups.backupdb -&gt; kMDConfigSearchLevelFSSearchOnly
    Indexing enabled. 

Please note: &quot;Indexing enabled&quot;.

In preferences pane of Spotlight one can see, that the Time Machine Drive is excluded as expected:

My Questions:
Is the output just a &quot;wrong&quot; output since the parent folder is disabled for spotlight? Or is the spotlight index essentially for TimeMachine to work properly? And if both questions will be answered with &quot;No&quot;, how to finally stop spotlight from index my time machine backups?
According to Apple, at https://web.archive.org/web/20180101183140/https://support.apple.com/kb/PH21902?locale=en_US

If you add a Time Machine backup disk to the privacy list, you will
continue to see messages that Spotlight is indexing your backup disk.
This indexing is necessary for Time Machine to function properly and
can’t be disabled. Spotlight does exclude from searches any items you
store on your backup disk that are not part of a Time Machine backup.