Huh. I just opened my Files app on my iPhone 12 and went to On My iPhone (which was 2-3 more taps once arriving in the app). I don't see many of my files though, just a few. Some PDFs and a Spotify folder. But I don't see my pictures there? Or are pictures no longer stored as 'files'? Or do you mean that the app has allowed access only to some local user files? It's not all local files. And it's not all non-system local files. And it's not all user files. In fact it is missing > 99% of my user-space files (specifically ones created with default-OS applications on device, by the user).

And if I make a Note in the Notes app, will it show up as a file in the Files app? Probably not, I would guess. Because the note probably isn't really a file anyway. So pictures aren't files, and notes aren't files. What would a file be then? Are files only PDFs? That's the only thing that shows up for me. I guess PDFs are the only things that are files then!

Super confusing experience. I'm a mobile app developer by the way - on Android. Android sucks at this too of course. But the iOS Files app is much too limited to enable users to 'get' the concept of a file.