Originally Posted by
DaveW
I haven't re-flattened any of the stones I've bought from dan's either, at least not since I started shaving. The ark doesn't cut fast enough once it's burnished to need perfection on the surface, and I'd imagine that even on the flattest finisher the highest rate of honing being done at a given point in time is at a small spot of the edge, and it's up to the skill of the honer to keep the work even on the bevel.
The same as any other tool.
Natural whetstone's stones are also flat (speaking specifically about the gray trans stone they call "black trans"), but they have a surface that is either more coarse or it might be straight off of a diamond saw. Good stone, though, just not something you can just lay a razor on out of the box like you can a dan's stone (though the dans get better and finer with use, like they all do).