Same saddle as my main road bike. And my other drop bar bikes have saddles that are basically the same shape, width, and length as my main road and gravel saddles.
Brooks C17 are on my gravel bike and main road bike.
A gravel bike is just a road bike for unpaved roads.
With that said, some gravel bikes can have seriously different geometry than a road bike and if you are significantly more upright then maybe a different saddle for your gravel bike would work well.
Is your setup on your road and gravel bikes basically the same?