That is his protocol to make sure you allow your new stomach to heal properly and that you dont do the wrong thing and damage it. The whole length of your stomach is a raw wound. Your stomach is swollen and numb so you cannot "feel" what is happening there so taking small sips of only liquids keeps fluids and nourishment moving through it effortlessly. Just do what he says, get off to a wonderful start and count your blessings! You will need the time to heal, rest, learn to manage what you do get to eat, sort your clothes into descending sizes, take walks, etc.