From the above example (apples⇢organisms), it is clear that during traversal of an upward generalization path, the correctness of individual edges is inconsequential to finding a good generalization for starting node (i.e., apples) once the first wrong edge (fruits↝vegetarians) is encountered.
a good taxonomy should not only provide a large proportion of correct edges, but also provide correct generalization paths, i.e., paths which are correct in their entirety.