Facing a similar problem, trying to detect id a iOS 13+ user already gave permission. Came up with this helper:

async requirePermission() {
  if (typeof DeviceMotionEvent?.requestPermission === "function") {
    try {
      const response = await DeviceMotionEvent.requestPermission();
      return response !== "granted";
    } catch (error) {
      return true;
    }
  }
  return false;
}

Here is a complete example and implementation:

https://codepen.io/snap/pen/pvzJxzX