Limiting Version Retention

According to the documentation we can set a policy to control the version retention. I’m interested in limiting the version retention so that if someone got unauthorized access to my files they wouldn’t be able to comb through the entire history to find private information. They would be limited to only recent private information.

I created a file in my config directory with the following contents:

$CONFIG = array (
  'versions_retention_obligation' => 'auto, 30',
);

If I am reading the documentation correct that should follow the default versioning policy but delete anything older than 30 days.

After adding that file, I find if I go to a file that has versions older than 30 days those versions still exist. I.E. it doesn’t appear to be truncating versions old than 30 days.

I wasn’t sure if the expiration happened immediately or on a cron job or something so I have waited a few days and still no luck. I also tried making a trivial change to make a new version (maybe it only expires old versions when new ones are created) and also no luck.

Can anybody point me to what I am missing? Thank you in advance.