I'm new to thinking about special and general relativity and I have no formal training as a physicist. However, I've been doing a bit of thinking about spacetime recently. I was wondering if "gravitational waves" provide evidence that spacetime accurately describes the structure of the universe. Or, in other words, do "gravitational waves" provide evidence that time exists as a 4th dimension in the universe (and what that implies about past, present, and future events in 3D space all existing with equal reality)?
Please keep in mind, I'm not asking for opinions (or dogmatic assertions) about the accuracy of universe-as-spacetime-continuum theory per se. I'm asking if "gravitational waves" logically imply the universe-as-spacetime-continuum theory.