- Home folder read/write access
- System folder media
- System folder mnt
- Microphone access and audio playback
- And more...
The Obsidian snap [1] is installed with the --classic flag, which also grants access to the whole home directory, but at least you have to consciously specify the --classic flag to grant this permission.
flatpacks have access to all my files, they would be useless without. And they are the only sensitive files in my computers
If you're running GNU/Linux, chances are you'll have hundreds, if not thousands, of pieces of software that run totally unsandboxed.
Yes, a very small minority of applications are unfortunately primarily distributed via flatpak or snap, and the distributors don't care about the user experience, so it's error-ridden and problem-ridden, but chances are you can get a "normal computer program" version of it unencumbered by such grossness.
Besides. They said "all software on your machine". That is trivially false, to a significant degree.