Because of how twists work, going first is the less desirable thing in battle-raps that haven't got a 'no flips' rule.
The one who goes second has an entire extra Round to show off the ability to flip lines back onto the other rapper in proper skill-rap, the usual thing is that the newer rapper gets to go second but sometimes an arrogant champion will demand to go second and go 'you first, bitch, if you got the balls to take me on'.
It is unheard of to fight to go first by saying the second guy is the brave one, but thanks for the baiting. It was cute.