Nothing like that is at all stated in any lore sources lol. Avatars? An avatar the size of a planet? That’s like saying a human’s body is his avatar, he has a spirit that goes to the Shadowlands right? So the body isn’t really a body, it’s an avatar.
Avatars are explicitly stated as being Avatars (like the avatar of Sargeras, holding a small faction of his power). You can’t just make an assertion that something is an “avatar” of something else because it has a spirit that can live outside of the body. That’s true of virtually everything in Warcraft.