Does not "Prevents deletion"

The module makes use of file usage data from core. There are known bugs with that API in core.
The module also supports the more robust entity usage module. I would recommend using that if you can.

Thanks for the quick response. I have those modules installed and enabled. This module detects that media is being used and warns the user, but does not prevent deletion. Is this working as designed?

So that warning is coming from entity usage module.

Media file delete will allow you to delete it if there is only 1 usage but prevents if there is more than, whilst entity usage warns if there is more than zero.

I would suggest that you:
* triple check the usage - if there's only one usage and its on the media entity you're deleting - its all working - happy days
* turn of entity usage delete warnings for media entities - looking at the code, it looks like this can be done from the entity usage settings form

Let me know how you get on

Oh and also, that warning is about usage of the media entity. This module doesn't have anything to do with deleting media - its to do with deleting the file attached to the media.

So I think there's a disconnect there.