Japanese naturals are porous. The stones that qualify for razors etc are usually very hard, and don't absorb water well.
Coarser or softer stones take up water more easily.

I have a Japanese natural which is ~6K. I also have a Nakayama on the way.

The ink of the stamps soaks into the stone, sometimes as much as 1 mm.
So if it is already flat, you can use the honing surface for a long time before you lose the markings.