Why chef sonnenschmidt calls the demi-glace sauce?

There is no chef named Sonnenschmidt who calls demi-glace sauce. Demi-glace is a French term that means "half-glaze" and refers to a rich, flavorful brown sauce made from reducing beef or veal stock, mirepoix (a mixture of diced carrots, onions, and celery), and tomato paste. It is commonly used as a base for other sauces or as a glaze for meats and vegetables.