Touch phase is moved when touch pressure changed

Question

I am trying to scale my object by a finger touch just like in Jelly Shift game. It should scale up/down when I move my finger up and down and it should stop when the touch is in stationary phase.

The problem is when I pressure the screen without moving my finger, touch phase changes to "moved" and my object scales down. The harder I pressure, the faster it scales down. I tried to clamp touch.pressure to 1 everytime it detects a finger on screen, but it didn't work. How can I ignore pressure of the touch and scale the object just by finger moves ? Thank you so much.

Note: I test codes on iPhone 7 Plus

Here I check the input by touch

private void CheckInput()
             {
                 if (Input.touchCount == 1)
                 {
                     _touch = Input.GetTouch(0);
                     // I've tried to clamp touch pressure like below but it didn't work
                     _touch.pressure = 1;
                     if (_touch.phase == TouchPhase.Began)
                     {
                         _isInputAllowed = true;
                     }
                     else if (_touch.phase == TouchPhase.Moved)
                     {
                         _isInputAllowed = true;
                     }
                     else if (_touch.phase == TouchPhase.Stationary)
                     {
                         _isInputAllowed = false;
                         Vertical = 0f;
                     }
                     else if (_touch.phase == TouchPhase.Ended || _touch.phase == TouchPhase.Canceled)
                     {
                         _isInputAllowed = false;
                         Vertical = 0f;
                     }
                     CalculateVerticalInput();
                 }
             }

I process the input below

 private void CalculateVerticalInput()
     {
         if (_isInputAllowed)
         {
             if (_touch.deltaPosition.y > 0.5f)
             {
                 Vertical = 1f;
             }
             else if (_touch.deltaPosition.y < 0.5f)
             {
                 Vertical = -1f;
             }
             else
             {
                 Vertical = 0f;
             }
         }
     }

Object scaling method

private void Scale()
     {
         if (_inputData.Vertical == 0)
         {
             return;
         }
         sourceScaleVal = (_inputData.Vertical > 0) ? _settings.MinScaleValue : _settings.MaxScaleValue;
         targetScaleVal = (_inputData.Vertical > 0) ? _settings.MaxScaleValue : _settings.MinScaleValue;
         transform.localScale = Vector3.MoveTowards(transform.localScale, new Vector3(sourceScaleVal, targetScaleVal, transform.localScale.z), _settings.ScalingSpeed * Time.deltaTime);
         PlayerHelper.SetCurrentScale(transform.localScale);
     }