I have a raleigh CX bike (appears similar in geometry to the specialized crux which I know is a true CX bike) and I did gravel riding on it this summer (including 150mile gravel event). It was fine. I'm not an expert by any means, but I believe common wisdom says if you're doing CX get a CX bike and it'll work just fine as a gravel bike, whereas a gravel bike is not super compatible to doing CX races.