Pulled pork should not be fully submerged in liquid during the slow cooking process to maintain the desired texture and concentration of flavors. Submerging the meat entirely can lead to an overly wet and mushy consistency, diluting the rich flavors developed during cooking. It's important to strike a balance by using enough liquid to keep the environment moist and flavorful without drowning the pork. This allows the exterior to develop a desirable crust, and as the collagen breaks down, the pork becomes tender while still retaining a satisfying texture.