Again everything obeys it. If there was something that didn't obey fundamental changes to spacetime itself we'd observe things like gravitational waves in a co

Again everything obeys it. If there was something that didn't obey fundamental changes to spacetime itself we'd observe things like gravitational waves in a completely different location and time to their visual counterparts. We do not see any evidence of this. So for any theory that states a change in the fabric of spacetime itself you can guarantee that everything must conform to that change.