What could be the reason for this, and how could we use a three-column layout in the Mobile App as well?
I have a Nokia 7.2 with 6.3 inch and 2240 x 1080 pixel resolution. My girlfriend has a Xiaomi Mi A3 with 6.1 inch and a resolution of 720 x 1,560 pixels. The behaviour is the same on both devices with the official Home Assistant app. Compared to browsers, the screen size is not fully utilized or does not scale properly.
The mobile app uses android system webview, check that is up to date and see if it resolves the error. If it does not then file a bug in the android repo and show both sets of screenshots to show it only happens in the android app.