Quick quote from T. E. Wilkerson; I think this has some bearing on Kornblith’s assumptions about natural kinds…
“… because there are no real essences that make rubbish rubbish, and tables tables, I cannot even in principle make sound inductive projections about rubbish as such or tables as such.
… the phrase as such is crucial. Obviously I can make safe predictions about the behavior of my table or rubbish heap under certain circumstances… But the point is that, in making my predictions, I am exploiting the fact that every object, or quantity of stuff, will belong to at least one natural kind, even if it also belongs to one or more non-natural kinds.” (p30)
i.e. all inductive inferences are safe (reliable) if they describe the behavior of natural kinds.