This is a perfect example of the need for physical comparmentation. Separate devices never connected through the same internet service. As far as devices go, to think you have separated “anything” on only one device, you’re living in fantasyland.
Statements like this make me want to learn phone OS development just so I can have a better understanding on what information an app can get from the OS. Honest question, why would an app ever need to know the SSID of a wireless network? The app should only care if there is a valid network connection, and then use it. I can see being able to know if it is wifi vs cellular so they can have the option to limit large downloads to wifi only. However, the SSID would not be necessary information for the app.
An example would be an app for associating a device without a screen on to a wireless network. Think IoT devices or Alexa. Saves the user from having to type in the SSID which is a pain.
IP address commonality is probably a major part of this, so using separate devices only helps if they are on different carriers and you never use wifi AND you don't allow location services or practically any other permissions.
With a single device, it's fairly reliable to use a vpn or multiple vpn providers and only log in to each account when connected to a given vpn.
