My Hall Effect Controller Is Drifting, I Thought That Was Impossible

Support gave you half the truth. Hall effect sticks cannot drift for the reason potentiometers do, because nothing rubs on the sensor, so there is no track to wear out. But drift only means the centre reading is not zero, and a magnetic stick can still get there in a few ways.

The most likely one in your case is the phone clip. If it holds the phone with magnets, it sits a few centimetres from the stick magnets. Any nearby magnet adds its own field to what the sensor reads, so the centre shifts. Test with the clip off and the phone away. If the 0.09 drops close to zero, you have your answer, and a clamp-style clip without magnets solves it for good.

The second cause is calibration. Magnetic sticks are calibrated at the factory to map the magnet's position to stick values, and that map can shift slightly after a knock, a firmware update or big temperature changes. A fresh calibration with the stick untouched usually clears a steady offset completely. 8BitDo publishes calibration steps for its controllers, and Ultimate Software handles firmware updates.

The third cause is mechanical. The spring and gimbal that return the stick to centre can loosen, so the stick physically rests a fraction off centre. If you can feel the stick sitting slightly tilted or loose, that is the issue, and recalibrating only partly hides it.

Steady offsets like yours are almost always the first two. Readings that wander from minute to minute would point elsewhere.