True, but that does seem to fly in the face of feat design. The only feats in the game that can be taken before they can be used are metamagic feats. Abilities that use a modification of character level as a baseline usually note having a minimum of 1.
In all honesty, I see two ways that this feat could be taken. One is that it should say "2 levels lower than normal (minimum 1)".
This idea that it would work at lvl 1 as you claim would be a horrible feat design. If they said "2 levels lower than normal (minimum 1)" Then the feat would be MORE POWERFUL when taken at level 1 and 2 and then become less powerful as you leveled.
Why would a feat allow a character to use positive and negative energy at the same d6 power output at level 1 and then suddenly your character "forgets" how to do this as he levels up? No, no way.
It seems to me they omitted "2 levels lower than normal (minimum 1)" on purpose to keep the feat from being unbalanced at levels 1 and 2.