Delay before first touch position changes on iPhone

I have a problem using Input.touches[0].position. Sorry if the problem is unclear, I find it somewhat hard to describe.

When I start touching the screen and very slowly start to move my finger the position returned by Input.touches[0].position doesn’t change immediatly, I have to move a little then it jumps to the current touch position.

This happens on iPhone, I don’t have any other touch devices.

Here is some testable code illustrating it:

using System;
using UnityEngine;

// attach this to a game object on the scene
public class TestTouch : MonoBehaviour
{
    private void Update()
    {
        if (Input.touchCount == 1)
        {
            // you have to add a GUIText component to the gameobject
            this.guiText.text = "pos: " + Input.touches[0].position;
        }
    }
}

Finally I just ignore the first delta, that is the first change in position, this solves my problem pretty well.