@Hollow7F not really, those saplings are usable as materials for wooden weapons, like magic staves, or bows, so the guy can just auction them off for tons of cash.
@degenerateafro it's just another "sense" like any other, but from what I remember, they lose all their PK skills when they die, and then have to level it back up. Plus as you saw there, the OHKO skill leaves you wide open for a counter. Besides, while they say it's due to the slash resist of being an undead, I think it's more about the skill being an insta "death" skill, and not only are those ineffective against undead, they have a notoriously low hit rate in most rpgs.