Why the spen does't provide z-axis?

I am trying to explore the possibility of the spen on my Note20. but i don’t know how it works. i assumed an accelerometer would give the three axis x, y and z but the event give only two x and y. I am not sure if there is a translation inside the device driver. That would mean that somewhere there js the raw data from the accelerometer. unless I am cometely wrong and there is something completely different inside.

You are right about the Z axis data. Because S Pen for Note 10/20, Tab S6/S7 supports BLE, accelerometer and 3D gyroscope. But the SDK only offers x and y axis data to third party applications.
S Pen is connected to the device by BLE (Bluetooth Low Energy), and the connection is managed by the S Pen Framework. And this Framework manages the translation between the stylus movement and app action.