I think fp4 didn't retroactively add baddy kills pre-points to the points when he made the change, so that guy didn't get credited in points for the 2k+ BKs he had before
You likely won't get any less than 1 point per baddy kill, I haven't tested it at all though

Edit: I just killed 1 spider and got 27 BK points? After that, all spiders counted as +1