It doesn't look like the linseed oil soaked very far in, maybe an eighth of an inch. At Mytraya* in Oregon they had a floor like this and on the sample piece they showed us the oil was soaked in almost half an inch. Mr. Universe tsk'd when I told him about that - evidently he had two books which disagreed on how to do it, or something like that. Might've picked the wrong one.
Grit does no good to any flooring, and this kind seems to be relatively fragile versus grit and scratches. It's kind of a tough deal because it doesn't show the dirt (being mostly made of it) so you don't tend to sweep as often.
*sounds-like. I can't remember how to spell it well enough to find the web site.