I'm not sure what you're talking about. A gravel bike is nothing more than a road bike with sufficient tire clearance for up to 32 or so gravel knobbys. Most of the bikes before 1985 would do that. I can't say that I ever even used special tires to ride gravel roads and just went from asphalt to dirt road without even thinking about it. And that's when a wide tire was 23mm.