Why touch.deltaposition takes reference of previous touch? (Legacy Input)

Unity Engine
,
1

I’m using Legacy Input, touch.deltaPositionto control virtual camera rotation.

In one script, camera only rotates when drag, but in another script, camera rotates right after I touch the screen and just begin the drag.

My code is very simple, the script 1 gives desired result, that the camera rotates only when I drag. During the test, all touches are 1 finger touch and drag.

I hope to know why in Script 2 with the virtual camera 3rd person follow mode, the camera rotates as soon as I touched the screen before I begin to drag.

Script 1, desired - CinemachineFreeLook

    private CinemachineFreeLook currentVCam;
    private float dragSpeed = 1f;

    public void Update()
    {
        if (Input.touchCount > 0)
        {
            foreach (var touch in Input.touches)
            {
                    currentVCam.m_XAxis.m_InputAxisValue = touch.deltaPosition.x * dragSpeed * Time.deltaTime;
                    currentVCam.m_YAxis.m_InputAxisValue = touch.deltaPosition.y * dragSpeed * Time.deltaTime;
                    break;
            }
        }
   }

Script 2, not desired - Virtual Camera, 3rd Person Follow

public Cinemachine.AxisState yAxis;
    public Cinemachine.AxisState xAxis;
    private float dragSpeed = 1f;
    public Transform LookAtTarget;

    void Update()
    {
        if (Input.touchCount > 0)
        {
            foreach (var touch in Input.touches)
            {
                    xAxis.m_InputAxisValue = touch.deltaPosition.x * dragSpeed * Time.deltaTime;
                    yAxis.m_InputAxisValue = touch.deltaPosition.y * dragSpeed * Time.deltaTime;
                    break;
            }
        }

        xAxis.Update(Time.deltaTime);
        yAxis.Update(Time.deltaTime);
        LookAtTarget.eulerAngles = new Vector3(yAxis.Value, xAxis.Value, 0f);
    }

Thanks very much.

2

I just leave Input Axis Name to blank, and everything is fine.