@HaltingBlooperYou can't look at their bodies as just projections though. They can blush, they can eat which causes a normal human like process, they can get slight food poisoning for a short time, ect.
It basically means that though it is a projection, it also becomes a hard mass that other living beings can touch and feel. My guess is that the body mimics what is needed for whatever process they are trying to achieve. Think of it this way, have we ever seen a home world gem cry? Will we ever? My guess is no. Why? Because they have no idea what that is. Why the crystal gems can is because they have seen humans do it and mimiced the reaction to express how they feel. The magic creates the nessassary items/body parts to do as they wish. Such as, Rose wanted a child so she made a womb for Steven. Amethyst likes to eat so her body creates what is nessassary for that. Since it is made of magic though, this is why it can be changed or bent out of shape for a certain period of time or destroyed in a proof because it is still an illusion but just a highly solid mass like illusion that magic keeps on tack. We have seen them get sore due to injuries. It is just that they feel things differently probably than human senses.
