Are you suggesting eath rocks "created water through fusion"? That would be pretty dumb. The earth rocks and the asteroids and the comets are all just material that formed our solar system.
So the water found in earth rocks and asteroids and comets all formed before this material collected into the spinning cloud that formed our solar system.
So you have not spoken at all to the source material and the new discovery in it.
And earths rocks are generally water poor compared to the amount of water on earth, which is how scientists know much (not all) of the water on our planet was delivered by asteroids and comets AFTER the earth formed.