Thunderbrd
C2C War Dog
That's already what it means. On Developing Leaders, it makes you start with no traits at all so you can grow into them. However, if you are not playing with DL, you're ONLY starting with no Positive traits and this is how you play with only your negative trait, unless No Negative Traits is also selected so you play with no traits at all. This was how you could play a game with only negative traits on if you wished.Perhaps the "Start with no Positive traits" needs to be changed to a "start with no traits" option?
It was how we kept this to the minimum number of options possible. The tooltip explains it, as Sakura Matou said.