How does adding one ingredient to a dish prevent another from burning?
There is only one way that adding an ingredient prevents another one from burning: it brings down the temperature.
Usually this is because the added ingredient has a lot of moisture in it.  Boiling off water, whether that water is in liquid or inside an ingredient like onions, requires a lot of heat energy, and while the water is being boiled off, the temperature of the cooking vessel drops towards 100C.
That's the case with the ginger in that recipe; ginger has water in it, and that water has to steam off, and will lower the oil temperature.  However, since the ginger doesn't have much mass, it won't lower it very much or for very long ... which is why the chef adds the sliced potatoes less than 30 seconds later.  The potatoes also have a lot of water, and they have a lot more mass.
Sometimes the ingredient will also lower the temperature because it is cold, and is being added to a cooking vessel with the heat turned off.  A common example of this is adding cold butter to finish a sauce.
Now, sometimes online chefs will tell you &quot;add X to prevent Y from burning&quot; wholly inaccurately.  If the added ingredient doesn't follow one or both of the criteria above, they're talking nonsense.