I'm not sure what the big advantage of naturally formed grinding stones is. In any case, sellers find it difficult to specify the exact grit. My impression: this is partly a lifestyle product.
However: one manufacturer of Belgian whetstones advertises that its stone does not create a burr. Also, it seems to me that there is a Belgian whetstone on every luthier's workbench. Maybe there is something to it after all? Amazing prices are also paid for Japanese natural stones.
In principle, they, like the artificial stones, also need to be dressed. However, some natural oilstones, such as Arkansas, are very hard and rarely need dressing.
I don't own any natural stone (yet) and can't say anything else about this topic.