When you move your sight away from the riser, it can affect the pin height. If you are using a fixed-pin sight, then moving the sight will change the point of impact. This is because the pins are set at a specific height in relation to the riser. If you move the sight up or down, it will cause the pins to be either higher or lower than they were before, which will result in a different point of impact.
If you are using an adjustable-pin sight, then you can compensate for this by making adjustments to the pin height. However, if you make too large of an adjustment, it can throw off your whole shot. So, it's important to be careful when making adjustments to your sights.