An endurance version of a CX bike is fair enough.
To me a gravel bike is not just a bike ridden on gravel roads because by that calculation, my fat bike is a road bike when I ride it on pavement and that's just silly. A gravel bike is a bike optimized for riding on gravel roads. Wider tires to roll well over rougher surfaces, drop bars to cover long distances efficiently and comfortably, plus gearing on the wide end of the road spectrum to handle often steeper hills and surfaces that don't roll as well as pavement.