iOS has 2 solutions to this. They have a push models where you “share” the file to the next app you want to use. And they also have a traditional file store model where all apps can request to save and request to load files.
Critically, apps can not directly read your files, they can show a button which will open the OS file picker and the user can pick a file to open which then provides access to the app.
This means that opening a game does not instantly expose all of your sensitive files.
> Critically, apps can not directly read your files, they can show a button which will open the OS file picker and the user can pick a file to open which then provides access to the app.
Unfortunately this model breaks down for any kind of file type that doesn't simply consist of a single, atomic file, e.g. various constellations of media files (playlists, subtitles, multi-part videos), multi-part archives, HTML files, georeferenced imagery with sidecar files, etc. etc.
iOS apps can be given access to files and folders created in other apps. I have no idea when this was added, I didn't use iOS between 3.x and 14.x, but it's there.
https://juno.sh/ios-file-system/ for some info about how it works from the perspective of an application that might need to access other apps' data.
Critically, apps can not directly read your files, they can show a button which will open the OS file picker and the user can pick a file to open which then provides access to the app.
This means that opening a game does not instantly expose all of your sensitive files.