BRNko My (non-expert) sense is that maybe several things are being confused.
One thing is the Sensors permission, which gates access to a variety of detailed sensor data: compass orientation, accelerometer, on some devices temperature, perhaps some day even humidity! Information: https://developer.android.com/develop/sensors-and-location/sensors/sensors_overview
Another thing is screen orientation. Knowing which way the screen is oriented does not mean that an app knows which way is North, or whether the room is humid. Information: https://stackoverflow.com/questions/24170424/android-orientation-with-sensors
Meanwhile, as Android graphics gets more complicated, with side-by-side apps on large screens, plus also the possibility of multiple screens, the concept of screen orientation is getting weaker and somewhat deprecated. Information: https://developer.android.com/about/versions/16/behavior-changes-16#adaptive-layouts
Overall, if a particular calculator app is adapting to different screen orientations without the Sensor permission, it may well be because the app is caught up with current best practices, and does not imply that the calculator app knows things it shouldn't.