VLC on iPhone detects some MP3s as albums and not others - why?

[tensigh]

I have VLC for iOS 2.8.7 on an iPhone 6 Plus. I have some radio broadcasts where I fix some of the ID3 tags then I copy them to VLC on my iPhone.
For some reason, some of the files (they're from the same source) get labeled as "music files" in VLC but most of them don't.
How does VLC determine what is a TV show / music file and how does it group them?
Anything I can do in the tags to make VLC group them together?