What does the Storage Manager setting actually do? I'm trying to understand what the Storage Manager option in the Storage settings is supposed to do. The text says "Remove photos &amp; videos" and I chose the option "Over 90 days old". So far, it hasn't done anything. My phone is an HTC 10.

I've found some articles introducing the feature that seem to imply that ALL backed up photos will be removed every 30/60/90 days.

In Photos, the "Free up space" option removes anything that's already backed up, regardless of age.

So does the storage manager option do what it says it does? When or how often does it run? Does it instead clear all backed up photos every X days?
According to this blog (though I don't find Smart storage on my device now on 8.1 but did see that in some earlier version)


  Smart Storage is the Android Storage Manager which allows you to automatically delete the files in your device memory that has been backed up in Google Drive. The feature can be specified by a time period of deletion to take place, options range from 30, 60 or 90.
  
  This indicates the time by which the photos &amp; videos on your device will be deleted after being uploaded to Google Photos


(Emphasis supplied)

I haven't used it so can't confirm that but is reasonable since "Free Storage" clears downloads and unused apps instantly

Edit: This doesn't work. Answer retained on OP's suggestions. Please see comments