Beware: The Swisscard phone app will reset your paper statement settings. This means you will receive your statements by paper if you don’t deactivate it (again).
It is written on their email Grey on White (a…h…)
Also remember to do it for all cards!
To add insult to injuries (?) it is not clear how it is set. What I’ve done is to enable and disable it again, otherwise the setting is unclear. If I open the app again it shows the same unknown status.