I think you’re confusing a few things. I’m not sure what you mean by mip0 here, and the volumetric lightmaps don’t do shadowing (except with capsule shadows).
With static lights, static objects get soft shadows. Movable get none.
With stationary lights, static objects can get either sharp shadows, or soft shadows (like the static ones) if you enable “use area shadows”. Movable objects can only get sharp shadows.
You could move your level a bit if the current volumetric lightmap samples placement is problematic.