I would get the "promotion" option, however he never would give me one. Maybe it is a level of work I have left until my next promotion he is not happy with. I will try seeing if the level makes a difference if he says yes or not. It is confusing because I have over half a bar as it is.
The level definitely makes a difference. Check out
this post from Twallan who is a guru when it comes to interpreting the game code.
EDIT: So there's not only the 75% performance bar requirement, but also there's a cool down from the last time you asked your boss.