How to actually use PreloadManager

I couldn't find much documentation on PreloadManager and how to use it.

I found this article
https://medium.com/google-exoplayer/media3-1-4-0-whats-new-ba1c9c17ee1a
when preload manager was introduced.

I know there's the shortform demo which uses PreloadManager, but the demo itself seems more complicated than it should be. It's using multiple players and I'm failing to understand why.

The article above metions:

Media3 ExoPlayer now supports preloading multiple media items to memory before adding them to the player, thanks to the new PreloadManager.

To me this sounds like it should be possible to have shorts preloading even with a single player, but maybe I'm missing something and there's a good explanation why the demo is using multiple players.

My end goal is to have smooth transition between short videos in view pager.