A point (Tianchi point) above the tip of the tongue is used to prevent the loss of true qi and connect Ren meridian. As far as I know, the tip of your tongue won't come off when you exhale. Fu You said this kind of kung fu is Taoist static kung fu, which is difficult to be explained by science. If you are interested in this aspect, you can refer to the principles and methods of static exercise for health preservation.