That view will show you all the media it recognized in a folder view. If you have any files that it does not recognize, it will not show them. You’re out of luck off you have something unusual (like a downloaded Rugby Union game). It. Will. Not. Show. It.

You have to put it in a library that's classified as "Other", and then it will show all video files it's capable of playing as regular media without necessarily requiring you to descend into the folder hierarchy view. I have several thousand home videos, YouTube downloads, and other "custom content" that's handled this way.

I have videos that I've pulled down with youtube-dl in mine. Like random 'let's plays', random concert footage, one off JRE episodes, etc. I put them in "videos".

I've accidentally put TV shows in the movies category and had them not show like you describe.