While FuzzyChef describes a correct mechanism, it does not apply to your video. You can stop peppercorns from burning if you drop, say, a can of tomatoes on them, but not by adding a teaspoon of ginger. You will also note that the next sentence in the video tells you to "quickly move on to stop these from burning too", the ginger clearly does not have enough thermal mass to stop the mixture from burning.
What is going on here is either sloppy language, or a misunderstanding of what is actually happening. Lots of chefs know what works, but not every one understands why it works.
The simple explanation is that food needs time in the hot pan to burn. And it is the total time spent there that counts, from adding to the pan, to the temperature going down through adding a sufficient mass of cold food. Adding the ginger does not stop the peppercorns from burning; moving on with the recipe quickly means that the peppercorns have not yet had time to burn by the time the temperature goes down.
There is a slight deviation from this in wokking, but this is not what we see in this video. With a wok, you add the new food to the small middle spot, to cook it quickly over high heat, while pushing the last batch of ingredients up the oblique walls, where it is at a temperature sufficient to continue cooking, but not enough to burn. In your video, the dish has not reached that stage, and the spices are all in the middle still.