Thanks for the quick response. That summary is correct. I was confused because I couldn't remember ever seeing that "from Package installer" note; I can't swear to it, but I thought downloaded APKs (like from APKMirror or something) usually showed "from Vanadium." And I know I've been blocked from installing in the past until granting Vanadium that permission.
So would the Vanadium permission basically just cover a situation where you launch the file directly from the "download finished" notification?
Edit: I just grabbed a small keyboard APK from APKMirror, and even tapping on it from Files got blocked due to Vanadium lacking the permission.
Edit2: (Sorry, was trying things as they occurred to me.) Seeing some strange behavior in Files. If I open Files, it automatically opens to the Downloads "category" (as seen in the Files sidebar that contains things like Recent, etc.). Trying to launch the file from here results in nothing whatsoever. Tapping it a few times sometimes shows the "ripple" effect indicating that I tapped it (oftentimes not). No message or popup. BUT, if I go to the Files sidebar and navigate to Pixel 4a > Download and then tap on the .apk, it is immediately ready to start installing. Is this normal/desirable behavior?