Yes. If a dwarf or blink dog dies in a fight with another monster it doesn't show up in your kill list. You can minimize the chance this happens, but you can't be sure until you're done. Still, imo this challenge is not bad as challenges go. I made it twice so far (barbarian and mindcrafter) and in my failed attempts I had made mistakes.
I think backstabbing can ruin it too. So I think it's best not to get backstabbing from Bart (and don't play orc).