How do I test if the MediaCachePreload plugin is working?

We are streaming vod hls from mp4 files on s3. We are using a stream name alias in combination with external AES-128 encryption. We noticed the load time for HD content takes 20 - 30 seconds if it is not pre-cached, and < 3 seconds if it is cached.

Obviously having viewers wait 20 - 30 seconds before content plays is unacceptable, so we need to pre-cache all our content in the Media Cache. It seems the MediaCachePreload plugin was designed to do this. We read the limited docs, configured it to what seemed appropriate (preload value set to -1 for entire file) and added some videos to the mediacachepreloadtargets.txt. We provided the path to the mp4 url on s3, and not the playlist file with the stream name alias.

We dropped in over 25,000 videos to the list, and it didn't seem to do anything. Plugin is installed. What did we do wrong? Our storage is not filling up on the wowza server like it should with 25K videos in the preload list.

Is it suppose to be generating all the ts files with AES-128 encryption applied? If someone could explain what exactly the MediaCachePreload plugin does, will it work in our use case, and why might it not be working? Thank you!