I'm not sure I understand why this is close at all. If I had to pick two cards that did not improve my hand to fall on the turn and river that would make me absolutely confident that calling this river bet is profitable, they would be a nonspade King and a nonspade Queen. I don't like talking about "leaking less money in these spots" when THIS particular spot is as good a spot for a 4th pair call as there can possibly be.